It sounds like something out of a horror film: 13 siblings, aged two to 29, allegedly held captive and tortured by their parents for years. When they did emerge from their home for rare outings to places like Las Vegas and Disneyland, they appeared underweight and pale in their matching outfits and identical haircuts. But on Jan. 14, after two years of plotting, David and Louise Turpin’s 17-year-old daughter escaped from a window and called 911 with a deactivated cellphone, police say. Out of fear, a sister who fled with her quickly turned back.

When police arrived at their southern California home, they found “several children shackled to their beds with chains and padlocks in dark and foul-smelling surroundings.”

And while more horrid details about the children’s prolonged captivity are expected to emerge in the coming days, one glaring question remains: How could this have gone unnoticed for so long?

HOMESCHOOLING

The children’s homeschooling likely contributed to their isolation, causing them to lack social interaction and giving their parents complete control over their education. When police arrived at the home, some of the children did not even know what a police officer was, The Associated Press reported.

According to California State Department of Education records, the house shared the same address as Sandcastle Day School, where David Turpin was listed as principal. For the 2016-2017 school year, Sandcastle Day School officially declared an enrolment of six -- all of whom were the Turpins’ children.

In California, private schools are not licensed, regulated or overseen by the state. Although such schools should be subjected to an annual fire marshal inspection, no such inspections ever took place at the home. One of the older boys, however, attended classes at a nearby college, but according to local District Attorney Mike Hestrin, the boy’s mother would drive him, stay in the hallway during class, and promptly take him home afterwards.   

NEIGHBOURS

While some neighbours have said that they didn’t realize there were children in the house -- which looked perfectly normal in its suburban neighbourhood -- others have said that they never saw all of the children at once. Those who did see them described them as timid and unresponsive.

Neighbour Kimberly Milligan told The Associated Press that the Turpins were intensely private and “standoffish.”

"I got an impression, that, you know, 'You stay in your lane, I'll stay in my lane," she said. "It was never, 'Hi.' Never a wave. Nothing."

The family also kept odd hours, Hestin added, staying up all night and going to bed shortly before dawn -- adding, perhaps, to neighbours’ lack of awareness of what was going on inside the home. The children, moreover, were often restrained and kept locked in separate rooms from one another.

MALNOURISHMENT

When police first met the 17-year-old escapee, she was so malnourished they say “she appeared to be only 10 years old.” Chronically deprived of food, the Turpins’ 29-year-old daughter also only weighed 82 pounds while their 12-year-old had the weight of an average seven-year-old, The Associated Press said. According to Hestin, the children’s malnourishment was so severe that it had caused stunted growth and cognitive impairment, which likely abetted potential psychological manipulation.

PSYCHOLOGICAL COERCION

The alleged combined forces of prolonged violence, intimidation and starvation would have made the children more susceptible to psychological coercion, experts say.

“The number of individuals who would immediately respond to an opportunity where they could get away is very small compared to the number of people who would have that paralysis and insecurity and confusion about what to do,” Dr. Bruce Perry, a psychiatrist at the ChildTrauma Academy in Houston, told The Associated Press. Perry characterized the courage necessary to propel the teenager to escape as “remarkable.”

"The power that must have been exerted to keep an entire family like that for so long must have been pretty sophisticated,” he added.

In similar cases that he’s worked on, Los Angeles attorney Ambrosio Rodriguez said that such families often create their own belief system.

“They develop a kind of cultish doomsday type of religion where the father becomes this mythical leader and the mother and children's duty is to serve the father,” he told The Associated Press. Such families, he added, often use older children to rear and indoctrinate younger ones, making them less likely to seek outside help.

And despite infrequent outings to places like Disneyland and Las Vegas, the children were otherwise cut off from the world. They were not even allowed to watch television or have playdates with other children, The Associated Press reported, likely enhancing both their isolation and their parents’ control over them.

Living under such isolation can create such physical and emotional weakness “that they are unable to free themselves, even if an opportunity arises,” Bellevue/NYU Program for Survivors of Torture director Dr. Allen Keller told The Associated Press. According to police, the children were allegedly routinely choked, beaten and prevented from washing and using the toilet.

Such victims of abuse, Keller said, often suffer from intense anxiety and are easily startled by strangers.

“The abuser has basically taken complete control of them,” he added. “It is a state of severe helplessness.”

With files from The Associated Press