Teddy Daniels
Teddy is the main character in the book. A decorated soldier, he is a US Marshall dispatched to Shutter Island by Senator Hurly to investigate what is really going on there and also to help with the search for a patient who has gone missing. Teddy also has a motive of his own in visiting the island; he wants to find a patient called Andrew Laeddis who was responsible for killing Teddy's wife, Dolores. Teddy misses Dolores badly and dreams about her almost every night, and still uses what he thinks she would do in certain situations as his guide.
For most of his adult life, Teddy was a soldier of some description but found himself a changed man after being part of the liberation force at Dachau concentration camp. The prisoners there had been tortured in the most brutal and atrocious way, and the soldiers who liberated the camp and saw this with their own eyes had no qualms about lining up the SS officers responsible and shooting them. Later, though, Teddy felt guilt about shooting unarmed men and decided that in the future he would shoot to kill only if his own life depended on it.
Throughout the novel, Teddy appears to be a diligent and skilled investigator. He reads people well and pursues leads to their logical conclusion. It is very easy to see why he believes something dangerous and underhanded is going on, which is why it is a shock when Dr. Cawley's asserts that Teddy is, in fact, Andrew Laeddis and was in fact committed to Shutter Island himself two years previously for killing his wife after she murdered their three children. It turns out that Rachel Solando, the "missing patient," is a figment of his imagination, created because he is unable to accept what Dolores did and overwhelmed with guilt about his failure to take her mental problems seriously. He has apparently been carrying on the same charade since his arrival.
Andrew Laeddis
Andrew Laeddis killed Teddy's wife Dolores with apparently no motive. He is the mysterious untraceable prisoner for whom Teddy is searching. Dr. Cawley asserts that Teddy and Laeddis are one and the same—both part of an elaborate fiction created by Andrew because he could not come to terms with having killed his wife after she murdered their three children. Andrew is a delusional man who believes everything he is saying and whose grasp of actual facts only comes to him in dreams.
Dolores Chanal Davidson/Laeddis
From Teddy's recollections of Dolores we learn that she was captivating and that he knew she was "the one" the moment he set eyes on her. Dolores is very attractive, a little bit emotional and somewhat needy. From Dr. Cawley, we learn that Dolores was bipolar with huge swings between euphoria and depression, and that she drowned all three of their children before sitting them dead around the breakfast table. Depending on which version of the story we accept, Dolores was randomly murdered by Andrew Laeddis, or killed out of anguish by Teddy/Laeddis, her husband.
Rachel Solando
Rachel is the escaped patient that Teddy and Chuck are looking for. She murdered her children and was subsequently committed to Shutter Island for treatment. She seems to be leaving clues and coded messages for Teddy about both her whereabouts and the evidence he needs to prove that illicit torture and experimentation is going on. Her picture shows her to be incredibly beautiful. In the end, it seems that Rachel is entirely fictional, her name being an anagram of Dolores' and her existence only in Teddy's head.
Chuck Aule aka Dr. Sheehan
Chuck, unknown to Teddy before the novel begins, claims to be a US Marshal, although he is unable to recall men that Teddy knew who worked out of the Seattle office with him. He has very small, delicate hands that seem incongruous until he reveals himself to be Dr. Sheehan, the missing doctor said to have headed to the mainland on vacation. Chuck appears to be on Teddy's side and to genuinely have his back, but is actually telling Dr. Cawley everything Teddy has confided and everything that happens during their investigation. Chuck has an easy, genial way with him that makes him "one of the boys" and allows him to banter in a way that would be inappropriate coming from anyone else. Chuck's job is to keep tabs on Teddy, and it turns out that he also is his doctor when Teddy/Andrew is on Shutter Island.
Dr. Cawley
Dr. Cawley is Chief Of Staff at Shutter Island and is very proud of the experimental psychiatry they are doing there. Since most of his work appears to involve heavily administering hallucinogens in order to make patients admit their crimes to themselves, it is somewhat controversial and shrouded in secrecy. Consequently, when it fails the patient in question is either done away with or confined to a solitary area in a straitjacket before undergoing lobotomy surgery. Although Cawley claims to be anti-surgery, and merely out-voted regarding its use, it is hard to believe that he is not fully supportive of it, because it allows his failures to be hidden and his program to continue. He is an intelligent man who has all the answers and all of the power when it comes to declaring a patient sane or not. He seems to have more affection for his car than for other people, and is distraught when Teddy sets it on fire as a diversion.
George Noyce
George Noyce was a patient on Shutter Island before getting transferred out. Once away from the island he began talking about the experiments being performed there and highlighting the lack of accountability. He was then seen as a problem and transferred right back to Shutter Island, where Teddy finds him battered and bruised after having been beaten up by Andrew Laeddis.
Trey Washington
Trey Washington is an African-American orderly whom Teddy and Chuck encounter at the start of the novel. Later, he tells Teddy that there is a ferry leaving the island the next and that he must be on it, after Teddy taunts him for taking orders from the racist warden. Like Teddy, Trey is a war veteran.
Dr. Rachel Solando
Dr. Rachel Solando is a woman in patients' scrubs whom Teddy encounters in a cave on Shutter Island. She claims to be a doctor who worked at Ashecliffe, until she discovered the barbaric experiments that were going on there. She threatened to expose the island, and was labeled insane and confined there. She warns Teddy against eating any food, smoking any cigarettes, or drinking any water on the island, as they may be dosed with neuroleptics.
Litchfield
Litchfield is an escaped patient on Ward C, who runs around tagging people "it." When Teddy and Chuck encounter him, he tells them about the invention of a new weapon called the hydrogen bomb, which implodes rather than explodes. Teddy later encounters a guard who is looking for him, and directs him to the place where Teddy and Litchfield spoke.
