Inciting Event: U.S. Marshall Teddy, who is on Shutter Island with his partner Chuck in order to investigate the disappearance one of the prisoners/patients from the mental asylum, meets the German psychiatrist Dr. Naehring and immediately clashes with him. Naehring accuses Teddy of being a man of violence and compliments him on his “defense mechanisms.” Teddy demands to see the staff files, but his request is rejected out of hand.

This is such a subtle moment (as is true throughout the film) that it’s easy to dismiss it. But particularly in retrospect (having learned the film’s secret at its end), we can see this is the moment where Teddy first engages with the main adversary—his own proposed insanity. But even for first time viewers who don’t yet know his sanity is on the line, it still provides the necessary turning point by appearing to be about Teddy’s investigation and the doctors’ passive-aggressive refusal to cooperate.

First Plot Point: While having to stay over on the island due to a hurricane, Teddy dreams of his dead wife, who disintegrates into ashes in his arms (despite being sopping wet). She tells him, “Laeddis is here.” Again, this is super-subtle (one of the subtlest First Plot Points I’ve seen that still remains effective), but it provides the shift that pushes Teddy out of the Normal World investigation in the First Act and into his own personal quest to find Laeddis—the man he believes is responsible for his wife’s death.

First Pinch Point: While sheltering from the rain in a mausoleum, Teddy tells Chuck about his wife’s death and his theory that Shutter Island is actually a place where horrific mental experiments are being conducted upon patients in order to turn them into “ghost” assassins. Chuck counters by suggesting the Shutter Island people are onto Teddy’s investigation and they allowed him onto the island for the sole purpose of trapping him and removing him as a threat.

Again, this works beautifully on two levels: the surface level of Teddy’s investigation in which he feels the pinch of the adversaries’ threat to his work and his life—and also the secret level, in which Chuck is insinuating an important point about Teddy’s sanity.

Midpoint: The morning after the hurricane, the power goes out, and Teddy and Chuck take the opportunity to sneak into the restricted Ward C, where the most dangerous patients are incarcerated. Teddy believes he might find Laeddis there; instead, he finds a severely beaten prisoner named Noyce, who had previously given Teddy information about the experiments that were being conducted in the island’s lighthouse.

This shifts the conflict on a number of levels. For one thing, it represents a significant shift in Teddy’s mental state—as represented symbolically by his manic lighting of matches (which he avoided lighting in the first half of the movie, presumably because of the connection to the arsonist Laeddis and the fire that killed his wife). It also presents new information about the lighthouse, giving Teddy a new goal and a way to move forward actively, instead of just reacting.

Second Pinch Point: Teddy believes Chuck has fallen to his death off the rocks. He climbs down, but finds no body. Instead, he enters a cave and finds the woman prisoner who disappeared in the beginning. She tells him she was originally a doctor on the island, but that she was imprisoned when she tried to speak out against the prison’s practices. She warns him the doctors will try to commit Teddy himself. This is the moment where Teddy shifts into full-blown panic over the danger in which he now finds himself. It perfectly sets up the Third Plot Point.

Third Plot Point: Teddy infiltrates the lighthouse in search of Chuck only to discover no sign of experiments. Instead, he is told by the head doctor that he is a patient, that he is Andrew Laeddis, and that his partner Chuck was really another doctor role-playing in an attempt to break through Teddy’s false reality. Not only does this offer a delightful horde of revelations, it also pushes the main character to a perfectly personalized low point. What could possibly be worse than having your goal of escaping incarceration be thwarted by the realization that you’re already incarcerated for insanity?

Climax: Teddy/Andrew finally remembers that his wife burned their apartment and drowned their three children—and that he shot her.

Climactic Moment: Teddy/Andrew speaks to “Chuck” in ambiguous terms that seem to indicate he has relapsed into his delusions—which leaves no other option for him than a lobotomy.

Resolution: Teddy/Andrew goes peaceably with the doctors in order to have his lobotomy.