Shutter Island

Teddy Daniels and his partner Chuck Aule have come to Ashecliffe Hospital on Shutter Island ostensibly to investigate the impossible escape of patient Rachel Solando, a woman institutionalized for drowning her three children. Teddy's real agenda is personal: he believes a patient named Andrew Laeddis, who murdered Teddy's wife Dolores, is hidden somewhere in the hospital, and he intends to find him. As a storm cuts the island off from the mainland, Teddy and Chuck explore the forbidden Ward C, where Teddy suspects illegal psychiatric experiments are taking place. There he meets another patient, George Noyce, who warns him that the whole situation is an elaborate setup and that Chuck cannot be trusted.

Separated from Chuck, Teddy takes shelter in a sea cave and meets a woman claiming to be the real Rachel Solando — a former staff psychiatrist who says she was locked up after discovering the hospital's illegal drug experiments. She warns Teddy that the food, cigarettes, and medication on the island have been laced with psychotropic drugs. When Teddy returns to the hospital he cannot find Chuck, and staff tell him he never had a partner. He makes his way to the lighthouse, expecting to find the site of the experiments and rescue Chuck, but instead finds only Dr. Cawley, the hospital's chief psychiatrist, waiting for him.

Cawley reveals the truth: Teddy is actually Andrew Laeddis. "Teddy Daniels" and "Rachel Solando" are anagrams of Andrew Laeddis and his late wife Dolores Chanal. Andrew has been a patient at Ashecliffe for two years, committed after killing Dolores, who had drowned their three children while suffering from severe untreated mental illness that Andrew, in denial and drinking heavily, had failed to properly address — including forgetting to lock away her medication before leaving on a trip. Unable to bear this reality, Andrew's mind constructed the elaborate fantasy of being a U.S. Marshal hunting his wife's fictional killer. "Chuck" then enters and reveals himself as Dr. Lester Sheehan, Andrew's actual psychiatrist, who has been playing along with the delusion as part of a last-resort experimental role-play therapy authorized by the hospital board, the alternative to which is a lobotomy. When Andrew, still refusing to accept this, grabs what he thinks is his service revolver to shoot Cawley, it turns out to be a toy water pistol given to him during therapy sessions. Sedated and taken to a cell, Andrew relives in his dreams the events leading to Dolores's collapse and the children's deaths, and finally wakes seeming to accept everything Cawley and Sheehan have told him — that he is Andrew Laeddis, and that he killed his wife after she murdered their children.

In the final scene, Sheehan visits Andrew again to check whether the breakthrough has held. Andrew appears calm and lucid at first, but then speaks to Sheehan again as "Chuck," insisting they need to get off the island — suggesting either a relapse into the delusion or a deliberate choice to feign one. The line is left ambiguous, framed by Andrew's own earlier musing about whether it is worse to live as a monster or die as a good man. Sheehan gives a signal, and Cawley and the ward's staff approach with orderlies and a cloth-wrapped surgical instrument, strongly implying Andrew is about to be taken for a lobotomy — a fate he may be choosing rather than live with the truth of what he did.

Scorsese films Lehane's ending exactly, then adds one line that changed how people argue about it.

In both, Andrew Laeddis is told the truth in the lighthouse — that he is not Teddy Daniels, that the investigation was a roleplay staged by his own doctors, and that a relapse means a lobotomy. In both he seems to accept it, and in both he is sitting outside with Sheehan afterwards when he calls him “Chuck” again and says they have to get off the island. The novel stops there: Sheehan signals, and Cawley and the warden come across with orderlies and something metal wrapped in cloth.

The film gives him one more line first. Before he walks away with the orderlies, Andrew asks Sheehan whether it would be worse “to live as a monster or to die as a good man” — and a stunned Sheehan calls after him, “Teddy”. Same last walk, with a question hanging over whether he chose it.