Shawn Hornbeck is back with his family after being held by an abductor for four years.
He was found Friday, though he seemed to have many chances to escape.
Psychologists say that leaving might not have been that simple. Shawn's parents say they're not asking their son about what happened. He has told them that for the last four years, he lived in fear.
"He thought that he -- [that] it would be the end of his life if he tried to tell anyone or do anything," said Craig Akers, Shawn's stepfather.
Hornbeck's alleged kidnapper, Michael Devlin, is expected to plead not guilty on Thursday. He is in jail and reportedly on suicide watch.
The moment the Missouri boy was kidnapped would have been vivid to him all those years, defining his behavior, observers say.
"The terrifying helplessness of the first moments of the kidnapping -- that danger seems very real," said Robert Pynoos of the UCLA Duke National Center for Child Traumatic Stress. "It remains real, and you then start to adjust to it."
Those adjustments often take the form of Stockholm Syndrome, which is named after a 1973 bank robbery in Sweden in which the robbers held employees hostage for six days and the victims became emotionally attached to their captors even as they were freed.
"Four bank tellers were held hostage for several days. During that time they became emotionally attached to their captors," said Greg McQuery, a former FBI profiler.
Some of the hostages protected the robbers from police when they left the bank, and one hostage had a relationship with her captor for years.
"There's a certain resignation that sets in that turns into adjusting, getting along with, even turning to captive as someone who provides for you, who you depend on," Pynoos said.
It may explain why Natascha Kampusch of Austria cried in August when she learned the man who had held her in a dungeon for eight years had committed suicide after she ran away, or why Elizabeth Smart first lied to police when she was finally found just blocks from her home.
"In our case Elizabeth was captive for two-plus months and there were times she did try to get away," Elizabeth's father, Ed Smart, told "Good Morning America" today.
When she tried to escape, she was threatened, Smart said, "and I think that that was very real to her."
Perhaps the most notorious case of Stockholm Syndrome involved Patty Hearst, an heiress who was kidnapped in 1974 at age 19 by political revolutionaries and later fell in love with one of her captors and helped them rob banks.
"I had no feeling at all," Hearst said in 1981. "And if they had come in and said now we want you to become terribly impassioned over the plight of chocolate doughnuts because they're so abused, I would have felt just as impassioned over chocolate doughnuts."
In a kidnapping situation, experts say that if there is sexual exploitation, then it only reinforces the feeling of danger and helplessness.
Every response by the hostage -- no matter how strange it may seem -- is aimed at making sure that threat you felt in the first place doesn't come back.
Stockholm Syndrome can happen in days, even less than a day. Ed Smart said he believed that Shawn's family should move on with its life.