Spain, 2000. A young man suddenly starts talking after appearing to be mute. He says he's called Nicholas Mark Randall, an American who was kidnapped four years earlier by the members of a sect.
To the surprise of the Spanish police, who suspect that he's an imposter and recidivist, his sister comes to pick him up and take him back to the United States, in Louisiana, where his family seems to recognize him.
The stories in the local media about this miraculous return alert the FBI, whose agent Jennifer Johnson who wonders more and more about Nicholas' true identity and the strange attitude of his supposed family.
Chameleon is inspired by the true story of Frédéric Bourdin, sentenced several times for usurpation of identity.