My bad opinions


Home Alone: a Post-Incident Review

Over the last few years I've been reading more and more about resilience engineering and all the related material when it comes to Learning From Incidents. This stuff has a way to stick with you and change how you think, and I found myself adjusting my perspective on a ton of things.

As this is the holidays, Home Alone is on TV a lot, and it's part of our household's tradition to watch the first two. Over the years, I've grown to know the movie pretty well—both the original English and the French dub—and generally know what to expect. But this year, I ended up looking at it with a different eye. My perspective had shifted from my usual watch where things go absurdly bad and a bunch of hurried careless people leave Kevin behind, and he's stuck at home to fight burglars.

This time around I noticed all the little checks that were in place but nevertheless failed. It turns out the movie is surprisingly detailed on all these things and made a lot more attempts than I initially thought to make it almost inevitable that Kevin would be stuck home alone. So the thing I decided to do was write an incident investigation the way I would do them for work issues. I can't interview people, but I got a fully recorded movie to work with, along with a script draft found online, which sometimes contains additional or conflicting information with what the movie contains.


I wanted to make a bit of a comparison with the more usual "root cause analysis" as we see it in tech, often based on the five whys, which consist of asking why on each problem until we narrow to the actual root cause. The issue with this approach is manyfold:

  1. it is arbitrary in how many times you must ask "why?" We stop whenever we actually feel comfortable with the fault we’ve found, not necessarily because it's good.
  2. it is reductive in the pathways it makes you follow because it tends to follow direct causal paths and missing important but indirect contextual cues
  3. it is done backwards from the known consequences of the incident, and is inherently going to be tinted by hindsight and outcome bias, making faults look obvious in retrospect when they were not at the time.

The approach I wanted to take instead is one where we focus on the messy details, to understand the challenges people were facing. One way to accomplish this is to do a deep dive in the events as they unfolded, and to do it from a perspective of local bounded rationality with the assumption that people are trying to do a good job. By re-constructing events as they happen in time, we can hope to reduce hindsight bias partially and lower the influence of outcome bias. Decisions have to be framed with the expected intents and the information people had rather than fully knowing the consequences after they had happened if we want to be able to have real impact.

Finally, this is not a serious study of anything. I did this because I found the idea amusing, but did not run this through that much care and didn't apply a ton of professionalism.

The Report

This report looks at events that have transpired in December 1990, where a family living in Chicago and on their way to France for Christmas ended up leaving their eight years old son home alone. The case has gotten worldwide recognition due to the creative ways in which the aforementioned youngest child managed to foil the plans of two burglars through creative and rather violent use of home supplies.

This text mainly focuses on the circumstances surrounding the incident. The world at large was surprised and outraged at the events, generally calling the family irresponsible for the events, and wondering why the police—who had been involved at the time this was taking place—apparently did nothing. We will cover a brief timeline of the events leading up to the youngest child being left alone, and what happened to reunite him with the rest of the family. We are not concerned about the improvised home defense systems that were improvised, and aim to shed enough light onto the incident to allow a reasonable chance at both prevention and timely recovery, rather than advocating for ways of booby-trapping a house, which we believe would be impractical to render safe. A brief analysis with recommendations will follow.


In late 1990, three brothers decided to reunite their respective families for the Holidays via a trip to Paris. The trip was being organized by the one brother living in Paris (also known to have owned real-estate in New York City), who was paying to fly in the families of his two other brothers. The events in question take place at the house of one of these two brothers, in Chicago, on December 22. Since they were leaving from O'Hare on the 23rd, both brothers' families were reunited there that night.

Altogether, the house contained 15 people: the parents who owned the house and their 5 children (including the one who was later forgotten), the other brother with his wife and 5 children (one of which was youngest of the bunch), and finally one of the daughters of the Parisian uncle. Things were hectic around the crowded house: sleeping arrangements had been reviewed and modified, and everyone scrambled to finish packing their suitcases before the end of the night.

The eldest son of the hosting family had ordered ten pizzas while adults were looking for voltage adapters before their departure on the following morning. It is reported that the youngest son, during that time, was feeling irritated by most of the remaining occupants, who were said to be dismissive of him—if not downright antagonistic—in all their hurry. These frequent conflicts had been a recurring theme in the household, and would still be a factor for this incident.

Everyone settles down for dinner: drinks are self-serve and all food is served with single-use cups and plates. Conflict erupts rapidly as the youngest of the host family sees his roommate (the youngest boy from the visiting family) drink Pepsi—which makes him wet the bed—while others ate all of the only pizza he wanted. In a fit of anger, he charged at his older brother, knocking him back and spilling milk all over the kitchen counter, the passports, and the plane tickets.

Home alone still: milk spilled over passports and tickets

The commotion propagates to the main table as the father gets up to salvage them, spills soda on the table, and the youngest kid gets wedged between his own father's chair and the wall at the dining table. While trying to dry the passports and tickets, the hosting father accidentally throws his son's ticket into the trash, before covering it with more similarly-colored napkins.

Home alone altered still: a ticket in the trash can, highlighted and with the name blurred

For pushing his older brother and being seen as the source of the conflict, the eight-years old attracts the ire of his entire extended family. His mother grounds him by sending him to bed directly, while also moving him from his bedroom to the attic: "fifteen people in this house and you're the only one acting up." This number fifteen will be critical in the next few hours, as we'll soon see.

One small victory for the child is that he will at the very least sleep alone, without his bed-wetting cousin.

During the night, strong winds blow over Chicago. At 4:37AM (10:37 UTC), the wind breaks a tree branch, which falls on an electric line and cuts all power to the house. This ends up resetting the hosts' alarm clock, a Panasonic RC-6067, which supports battery backup power. Unfortunately, this backup power source failed, and the family misses their wake up call.

Home alone altered still: the parent's alarm, highlighting the model and battery backup

At 8:00AM (14:00 UTC) sharp, two airport shuttles show up at the house, the driver confused by the lack of visible activity indoors. Their knocking on the door manages to awaken the host family's mother, who in turn alerts everyone about the situation. While everyone gets dressed and the household turns frantic, their across-the-street neighbour's kid—with the same age and height as the host family's youngest—invites himself into the front-yard, and starts talking with the shuttle drivers, who were loading the luggage that was all ready.

Inside the house, the mother starts delegating work. She approaches the oldest daughter of the French uncle, an adult attending Northwestern University (but who we suspect still sits at the kids' table and shall do so until she's 37) to do a headcount of everyone entering the airport shuttles. The father of the household is asked to retrieve the passports, which he had placed in the microwave to dry.

Kids start pouring out of the front door while their neighbour is already in a shuttle, asking tons of questions to an exasperated driver. The headcount is done by having the kids line up in front of one of the vans, the same one the neighbour is in. While the eldest runs the headcount, one of the kids randomly mentions numbers in an attempt to confuse her. She ends up skipping one of the girls and counting herself twice due to the interruption, and believes the neighbour (who is facing backwards and rummaging through someone's luggage) is one of the kids from the current household. The end result is that her headcount lines up properly: 11 kids as expected.

Home alone altered still: the headcount scene

Headcount sequence, with the neighbours' kid highlighted. Note that the headcounter arrives on the scene from the left, with the imposter already in place to the right.

She divides everyone into the two shuttle vans, but by the time the neighbour's kid turns around to reveal himself, she's already on her way to the other van and does not notice that she counted him as one of their own. The four adults exit the house and lock behind themselves. One of them mentions that they only have 45 minutes to go to catch their flight. Before the mother enters the shuttle, a working lineman announces that power is back on, but that the phone lines will remain cut for a few days.

In the shuttle, the mother asks the young adult to report on the headcount. She reports: "Eleven including me. Five boys, six girls, four parents, and a partridge in a pear tree." It's unclear whether she actually took the time to note the genders of everyone she counted, or if these were attributed post-hoc by believing the count to be exact.

The adults are divided up, one from each couple in each shuttle. It is important to point out that the act of dividing groups like that gives an immediate rational explanation for not being able to see any of the kids in the local shuttle: the count is correct, therefore the kid has to be in the other van. This can be believed regardless of whether the kid is there or stuck at home.

In the next scene we see the entire family running through the airport. The adults are constantly looking back; some hold the hands of their younger children while one of them literally carries the youngest one of the bunch in his arms. They make it to their gate at the last minute, where the father hands all the tickets (minus one, which was destroyed) to the airline employee.

She mentions that the remaining seats in coach are singles. Seats are unassigned there, and since the parents are flying in first class, they'll be set aside. The employee counts people rushing in, making sure that all tickets and people match up in number only. Here we have a discrepancy between the movie and the late script draft that was available; in the latter, no ticket is ever mentioned as being destroyed, but instead, the airline employee is reported to get an exact count (11 in coach, 4 in first class). In either source, everything looks normal to everyone involved, and there is no signal or alarm to make anyone suspect that anybody is missing.

Home alone still: the airport's quick headcount scene

Airport employee counting people as they enter the boarding tunnel, making sure their number matches tickets.

Everyone instead appears to be relieved that they managed to make it at the last moment, while the stewards rush everyone into their seats to leave on time. One of the parents mentions hoping they forgot nothing. Of course, by now everyone in the audience is aware of the irony that the youngest of the household has been left behind, unaware of all of the commotion by having been isolated in the attic, alone and fast asleep.

It takes a few hours before the mother suspects something is wrong. She has the gut feeling that they forgot something, and discusses it with her husband. They go over a mental checklist of items they had to cover and might have missed: coffee machine, locking up, closing the garage. Indeed, the husband had forgotten to close the garage and he figures that's what was missing and making his wife uneasy. She settles back down, only for the feeling to linger. She thinks for a few seconds more before realizing what they forgot is their son.

The adults are dismayed on the flight, blaming themselves and feeling horrible. They have tried reaching home through the captain's phone, but since it's out of order at their house, they're stuck waiting. Some of them try to minimize the guilt: "We'll call when we land", "we didn't forget him, we just miscounted", but the mother is still distraught and showing remorse.

As soon as the plane lands, the family rushes towards public phones. The mother gets her phone book out (a 2-inch thick document) and starts dispatching everyone to call contacts on their street. She personally calls the local police department to ask them to reach out to her son. They instead dispatch her to the Family Crisis Intervention center, where she asks for a check up once again, only to be redirected to the police. While she handles the bureaucracy, the rest of the family reports not being able to reach out to anyone. Apparently the whole neighborhood (at least those whose phone numbers they have) are out for the Holidays.

Finally, the police department sends an officer to the house, who knocks on the door. Since the child was afraid of one of their neighbours he had just encountered, he refuses to answer. The police officer, seeing no one and no damage, declared the house safe and asked for the parents to just count the kids again.

Ultimately, the family had to focus on getting back home as soon as possible to do things by themselves. No flights are available, not even private ones, until Friday morning, two days away. They end up dividing up into two swimlanes to help resolve things: the mother will remain at the airport as a standby to grab the first flight to America she can get, while the rest of the family will go to the home they were expected at in Paris to try the phones some more, at least until Friday when they can then fly back.

Once at the Parisian home, the father has trouble reaching anyone actually speaking English over the phone, and when he does they're all away for shopping or just not home. Some of the children feel bad about it, while others (mainly those who had ongoing quarrels with the one left behind) see it as some sort of well-deserved retribution with limited concerns otherwise ("we have smoke detectors [and] live in the most boring street in the United States where nothing dangerous will ever happen").

This appears to be the end of efforts as we know them from the family's side. The mother, still stuck in Paris, is haggling to see if she could trade or buy tickets from other travellers to make it home faster. She finally manages to trade a place for jewelry, cash, and first class tickets later in the week, and can board towards America.

Interestingly, by the time the adults have given up on reaching neighbours, it appears that phone communication was established back to the house since the child stuck home alone manages to order pizza. It is unclear why the rest of the family in Paris appears not to have tried again (or if they did whether they missed the child's presence who was running errands), but the phone isn't of consequence for the rest of events. There are various possible explanations ranging from the predicted time given by the worker at their door to having tried other ways to do things, but we have no information regarding what they are.

By December 24th, the mother had reached the United States via Dallas and was by then stranded in Scranton, but couldn't make it any closer to Chicago due to everything being booked, once again. By then she's been awake for about 60 hours. She meets a man in a Polka band who offers to drive her home in the back of a Budget rental moving truck while on their way to Milwaukee, which she agrees to more out of desperation (she mentions selling her soul if she must) than love of polka.

She makes it home a bit more than half a day later, on Christmas morning. The rest of the family drops home from their Friday morning flight a few minutes later, to the two others' surprise. The child makes peace with everyone, and describes his period home alone as thankfully pretty uneventful.


This story shows one of the typical "perfect storms" that are characteristic of surprising incidents:

Of particular interest here is how many planned fail-safes and checks were in place. Take any of these elements out and there's a good chance that nobody would have been left behind. All the tickets being intact would have prevented bad counts at the airport, a non-failing alarm would have removed hurry and pressure, the neighbor's kid not being around would have made the van headcount effective, and so on. All the items in the list needed to happen to be sure for one child to be forgotten.

We have to consider the context in place. If nobody thinks they could forget a child behind as an actual possibility, their focus is going to be on making sure they just make it on time for their trip and preparation. The various checks and headcounts would usually work, and just seeing the children would have one assume that they would notice any problems that would come up. This self-assurance, the divided vans, and absolute rush to make their flight had everyone focused on something else when they believed the headcounts to be good and complete. The race against the clock at the airport and unassigned seats in the plane did not help either.

The time pressure usually brings in compromises: not all work can be done as diligently since doing that would take too long. Hence, there has to be a tradeoff to try and get a reasonable output within the constraints. To minimize losses, they delegate tasks such as the headcount to others they believe trustworthy. An important step done is to still check back with each other to validate that everything has gone according to plan. Rather than removing the failsafes or dropping tasks, they reorganized the work to make sure everything still happens to the best they can. Obviously these pressures reduce the amount of attention that can be given to each task and a few were forgotten, such as closing the garage doors, to name one.

This is important to point out, because these compromises are done out of good intentions in an attempt to make things work. This means that any fix that focuses on adding safety checks that are time consuming risk, in practice, to see that fix omitted by the people in a hurry.

One thing that happens later, on the plane, is that feeling that something is wrong, not properly in place. This sort of intuition is typical of people slowly but unconsciously reevaluating their model of the world and understanding based on observations. Something clashes, but the amount of evidence has to add up until it tips the scales of what is expected and currently understood. The child's parents are aware of the rush and that they might have forgotten something, and they both recount things they've been doing over the morning to find what might be wrong. All their guesses are more mundane (and maybe considered more likely), and since none of them add up, the mother ends up realizing the problem: one child is missing.

They now enter recovery mode, where the intent is to fix the problem they have just identified. The first reflex is to try and reach out by phone, which they will keep on trying to do for hours. During down time, they blame themselves a lot. Furthermore, prompt recovery was rendered difficult:

These events unfold in 1990, where for the most part, if you don't know someone's phone number, you just don't really get an easy way to reach them out rapidly. What we see here is the family trying the whole playbook, and opening up new swimlanes to get back to Chicago ASAP: the mother staying standby in hopes of getting home faster, and the rest of the family waiting on a certain result by Friday morning. To go faster, she trades her jewelry and tries to negotiate with other passengers, and ends up riding hours in the back of a truck with strangers. Still, they end up home at the same time, to a child who was fortunately safe and healthy.


Although the main focus of this report is to shed understanding into how events unfolded, we nevertheless include recommendations to prevent similar incidents from happening in other situations. We divide up the suggestions into two categories: preventative means to avoid being in a rush, and organisational approaches to cope with an emergency rush better.

As Prevention

We've identified the following adjustments that could be done at a minimal cognitive cost and may make a difference:

It's interesting to point out that the checklist wouldn't have solved this incident in this case; the headcounts were successfully (albeit incorrectly) completed. Similarly, the other preventative measures only lower the chance of such incidents from happening but do not negate it: a family could be staying at a different place where their clock isn't available, a last-minute airplane model change could throw off buddy systems, and a family member might get lost elsewhere than their home (i.e. at the airport or at destination).

In Action

We have special interest in providing measures that could be used in a rush. It is important to point out that any method that is seen as a "redundant" check that takes more time is likely to be ignored by people in a rush: they did a check, they're short on time, and things are gonna be good enough. As such, we avoid suggesting anything which is equivalent to "take more time and think harder" since they are not considered useful for high-pressure/high-stakes circumstances, and tend to be policies geared for work-as-imagined rather than work-as-done.

There is in fact a single recommendation the author could come up with that might help prevent another home alone situation: redundant awareness and responsibility. We propose what is in effect a "pod" system: each adult is assigned two to three children (ideally theirs since they already have an inclination to care for them), and each child in the pod is made aware of who else is with them. People in a given pod should put their luggage together, have their tickets handled by their responsible adult, and sit together as much as possible.

Having this shared understanding where people in a group have to cover each other lowers the amount of things they have to keep in check within a large group, minimizes the chance of adversarial relationships between relatives from interfering with the process, and lowers chances of plausible deniability around seating arrangements. It would also—we hope—increase chances of successful early detection of anything going wrong, from missing luggage to lost children at any step of the way, whether at home or the airport.


So that's it for my post-incident review. I believe that having a focus on how things were done and how they unfolded has highlighted that the vast array of checks put in place are likely going beyond what most people would do already.

The preventive fixes I suggested are contextual and could all also fail individually, as pointed out in the report, but I believe that they are far less brittle than just suggesting things like "change the battery before leaving", "don't leave a milk container open", or "don't leave tickets in the kitchen area" which would come as rather easy potential suggestions from a five whys approach. There's also an easy suggestion to make in trying to reduce the amount of conflicts within siblings and cousins of the family, but I do not feel it is very realistic to provide a fix for that (spoiler alert, most of these easy checks that are done through looking backwards at the incidents and finding faults tend to lead to these easy but brittle fixes that wouldn't have worked in a second movie).

There are much simpler scenarios where things could have failed, such as a kid making it to a correct headcount, then having to go to the bathroom before leaving, and doing so with no adults seeing them. This, once again, could have happened either at home, at the airport, or anywhere in-between. Emergency and rush situations can be created easily as well: one of the shuttles could have gotten a flat tire, a pick-pocket or accidental dropping of ticket while accessing other papers, someone could have injured themselves on ice, the fallen branch that destroyed the power line could have laid across the street and slowed things down, connecting flights could have been delayed, someone could lose a bag, and so on.

The movie demonstrated that the family, in general, was quite apt at verifying things, delegating authority, keeping in sync, and finding multiple solutions once a problem was identified. They were ready to a greater extent than a lot of people I know (props to the mom for carrying this large of an address book to go meet family), but knowledge of the outcome (they forget a kid) tends to define judgment (they have to have been irresponsible!)

I believe the most effective option is the pod system, which is a strategy that would highlight breakdowns faster and allow prompt action at limited cognitive cost with minimal planning. Having multiple people involved in each group with redundant responsibilities increases the likelihood that any one of them notices what might be wrong, especially if the adults are overwhelmed dealing with things only they can do. Specifically, this approach shows promise regardless of what happens to an individual, not just being forgotten at home.

Finally I would like to compliment Kevin on his solid infosec skills in never mentioning he was left home alone, despite that potentially speeding up someone helping him given the circumstances. I am also a bit disconcerted how not one but two dads could potentially make a plan by which they were not all at the airport at least 5-8 hours ahead of their flights, which would have had everyone wake up before 4am and have avoided the power outage, but this is meant to be a blameless report after all.