Ten years later, Mrs. Underwood arrives at the school to pick up Josh, the son she was carrying when Billy disappeared. A group of teachers is waiting for her. The group parts, and she sees Billy sitting on the swings from which he disappeared ten years before. They boy does not appear to have aged.

Some time later, Scully examines the boy - who hasn't spoken a word since his return - as Doggett and the local sheriff look on. When Scully emerges from her examination, she tells them that Billy is exactly what he appears to be: a healthy seven-year-old boy who was born 17 years ago.

Despite these careful overtures, Billy remains silent. Mrs. Underwood takes exception to Doggett's approach and takes the boy out of the room.

In their wake, Scully and Doggett argue about Billy's mysterious return. Scully cites precedent from the X-Files to support the impossible nature of Billy's condition, but Doggett strains to find a "rational" explanation for his lack of aging.

Meanwhile, the Underwoods bring Billy home. The family dog -- a German shepherd -- has a hostile reaction to the newcomer. However, the barking doesn't faze Billy, who is too busy staring menacingly at his younger brother, Josh.

Back at the hospital, Scully has learned that Billy's current medical records are identical to what they where 10 years before. Doggett remains skeptical of any paranormal explanations. He prefers to focus his energies on the case file on Billy's disappearance, specifically on Ronald Purnell, the young man present when Billy disappeared.

That night Billy into bed sneaks out of bed. He hears his parents arguing about him. He walks down the hall with a hunting knife in his hand and slips into his brother's room.

Doggett visits Purnell's trailer to invite the man to visit Billy Underwood. Purnell appears confused by the attention and asks to be left alone. The agent returns to his car, removes a photograph of a young boy from his wallet and stares at it.

Mrs. Underwood looks for Billy. When she checks Josh's room, she finds the knife stabbed into the mattress. There is blood on the knife and on Josh's pajamas, but he appears uninjured. Billy stands on the other side of the room, staring intently at his brother.

Later, the sheriff tells Doggett and Scully that the blood found on the knife was Billy's, although he also seemed uninjured. Scully recommends removing Billy from the home. Doggett argues that the boy needs the familiar surroundings to work through his trauma.

The agents point out a strange symbol -- it looks sort of like a thinner version of the Blair Witch logo - on the knife's handle. The sheriff tells them that a psychic consulted at the time of Billy's abduction drew the same symbol in connection with his disappearance. Billy also scribbled the symbol during his interview with Scully.

Mr. Underwood loads Billy into the family minivan to for a psychiatric appointment. When he gets into the driver's seat and looks back, Billy has disappeared.

Billy appears in his brother's room. Josh screams.

Purnell leaves his trailer. His mother's boyfriend shows up and hassles him briefly, so he takes off into the woods. He digs a hole and unearths a small human skull. Billy is dead!

Scully and Doggett bring psychic Sharon Pearl to the Underwood residence. Although Mr. Underwood is frightened for Josh, Doggett tells the father that he has to save his whole family from the damage Billy's abduction caused.

When Mrs. Underwood brings Billy to meet with Pearl, the psychic immediately suffers a powerful vision. She tells them that powerful forces have drawn Billy to his brother's side. The forces in question are coming through Doggett -- as she tells the agent, "You lost someone just like Billy."

After making this pronouncement, Pearl begins speaking unintelligibly goes into convulsions. The mysterious symbol appears on her forehead.

Purnell's mother's lowlife boyfriend harasses the younger man. He threatens to "tell them what you did to that little boy."

An ambulance takes Pearl to the hospital. Doggett tells Scully that he is skeptical of the psychic's "performance." Scully plays a recording of Pearl's seizure-speak backwards and the agents hear a child's voice singing a lullaby.

Purnell's car pulls up nearby. Billy appears in the passenger seat as Doggett walks over to investigate. Panicked, Purnell drives off. Doggett chases him on foot while Scully drives around the block to head off the car. When the agents look inside Purnell's car, Billy has disappeared again.

Josh and his father stop at the gas station. When Mr. Underwood goes inside to pay, Josh sees a man across the street leading a pony into a trailer. He gets out of the car to look at the pony.

The boy puts his hand through the trailer's slats to pet the pony. Someone inside the trailer grabs his hands. Josh screams.

The trailer bears the mysterious logo connected to Billy's abduction.

Scully tells Doggett that it is impossible for Billy to have been in Purnell's car, but Doggett knows what he saw. The sheriff says Josh has gone missing as well. As Scully goes to talk with the Underwoods, Doggett decides to talk with Purnell.

The young man claims he doesn't know how Billy got in the car. He tells Doggett that he went to the Underwoods because he had to see for himself that Billy was back.

During their conversation, Purnell flashes back to seeing Billy bound and gagged in a cage under some floorboards. He tells Doggett that he didn't hurt the boy -- in fact, he sang so Billy wouldn't be afraid. Doggett asks Purnell to tell him who was involved.

The agents and the police race to the pony farm. They find Josh bound and gagged in a hidden cage beneath the horse trailer floor. Doggett chases the real killer -- Purnell's mother's boyfriend -- into the woods.

Doggett briefly sees Billy standing nearby, but the boy quickly disappears. When Doggett examines the spot where Billy was standing, he finds the half-buried skull Purnell unearthed earlier.

Later, after they unearth a skeleton, Doggett doesn't want to believe it is Billy's. Scully assures him that the forensic evidence will confirm his identity despite the fact that it seems impossible. She reminds her partner that he succeeded in stopping the killer from hurting any other children.

Doggett ponders Scully's words as the Underwoods come to grips with losing their son for the second time.