An 8-year-old American boy wakes up alone in a rice paddy in a rural Chinese province with no idea how he got there. Details start to emerge when the boy, who calls himself Jacob, recalls that his hometown is Arcadia, and an Immigration agent, J. Martin Bellamy, takes him there. The home he claims as his own is occupied by a 60-year-old couple, Henry and Lucille Langston, who lost their son, Jacob, more than 30 years ago.

While they look different, young Jacob recognizes them as his parents. Lucille is overjoyed at the seeming miracle of her son's reappearance. Henry is reluctant to accept that Jacob is back. Those closest to the family want answers, including Sheriff Fred Langston, whose wife Barbara drowned 30 years ago while trying to save Jacob, and Fred's daughter, Maggie, a local doctor. Pastor Tom Hale seeks a spiritual reason for what's happening in his community. When things take an even more shocking turn, Maggie's life-long friend, Elaine Richards, finds herself drawn into Arcadia's growing mystery.

The Langstons, especially Sheriff Fred, are forced to confront secrets from their past they'd rather leave buried when Bellamy pushes to have Jacob's tomb exhumed. Maggie agrees to help Bellamy in his investigation, and Pastor Tom reaches out to Jacob, his childhood friend. The Richards family adjusts to Caleb's return, the second for Arcadia. But unlike Jacob, Caleb claims he has no memory of his passing.

The exhumation of Jacob's crypt doesn't solve any answers. Bellamy's suspicions turn toward Caleb as he discovers his criminal past and current mysterious behavior. The townspeople start reacting from fear, despite Pastor Tom's council, but even his faith is shaken by the arrival of another visitor.

Bellamy and Sheriff Fred form an uneasy partnership to find Caleb, who has gone on the run after Dale's cuddle. After Jacob suffers a seizure, Maggie gives him a checkup at the clinic and is shocked by what she finds. Pastor Tom adjusts to the unexpected presence of his old love Rachael in Arcadia.

Bellamy and Langston fear the FBI will descend upon the town soon because of the bank robbery and then all of the returned will be taken away, even Jacob. They pressure Elaine for her help in recovering the stolen money to prevent this from happening. Pastor Tom takes Rachael to see Maggie because she is not feeling well and Maggie discovers something that shocks her. Bellamy suffers from nightmares of a previous lost child.

Maggie turns to a man from her past, Dr. Eric Ward, now working for the NIH, for answers to Arcadia's mystery. She insists Ward is there as a friend, but Bellamy is suspicious of any outsiders. Rachael's secret falls into the wrong hands. In the wake of recent events, Pastor Tom and Bellamy try to reassure Arcadians they have nothing to fear from the returned, but some residents have other ideas.

With the help of Bellamy and Sheriff Fred, Tom leads the charge in the search for Rachael, but her situation becomes increasingly dire as her captors grow more desperate. Maggie and Dr. Ward continue their medical research on the resurrected subjects and a series of shocking discoveries sets them on the brink of a game changing find, however, their focus shifts when Arcadia is suddenly in the throes of an epidemic.

The town of Arcadia is in a state of chaos when the return of the deceased reaches a critical mass. Bellamy has no other choice than to ask for outside aid which backfires when Sheriff Fred steps in with his own agenda, triggering a siege on the town that no one saw coming.