The film is based on the novel of the same name by American novelist Dennis Lehane. In 1954, federal police officer Teddy (Leonardo DiCaprio) and his partner Chuck (Mark Ruffalo) came to the Shutter Island prison for mentally ill prisoners near Boston by boat to investigate a bizarre disappearance. Rachel (Emily Mortimer), a female prisoner who killed her own flesh and blood, mysteriously escaped from a heavily guarded cell and hid deep in the isolated island. Teddy suspected that the prison's attending psychiatrist John Cowley (Ben Kingsley) deliberately concealed the inside story, and revealed to Chuck that his real purpose on the island was actually to find the administrator who set fire to his wife Dolores (Michelle Williams) and to expose the crime of the US government using mentally ill prisoners for human science experiments. But as the investigation deepened, the truth became more and more confusing...