Justice Wargrave is a cold, "reptilian" man who takes it upon himself to gather evidence after the first few deaths. He tells each person why they might be the murderer. Justice Wargrave fakes his death with Dr. Armstrong's help and is actually the murderer and the last person to die on the island by taking his own life.
Vera Claythorne is a former governess for a child who stood in the way of her lover's inheritance, preventing their marriage. She has been hired to be Mrs. Owen's secretary and is tormented by the nearness of the ocean because she allowed her charge to drown. She is supposedly the 10th and last person to die on the island, hanging herself in despair for her lost lover.
Philip Lombard is a panther-like, athletic, and heartless army captain who allowed 21 men in his company to die because they were African natives. He thinks he has been hired to observe the guests on the island, carries a revolver, and doesn't let the other guests push him around. He helps search the island for Dr. Armstrong, and is the supposed ninth person to die, shot with his own gun by Vera Claythorne out of her fear that he is the murderer.
Ex-Inspector Blore is a former police officer supposedly hired by Mr. Owen to come to Indian Island and prevent the theft of Mrs. Owen's jewels. He arrives under the alias Mr. Davis, but admits his real identity early on. He is a big, courageous man, the only person brave enough to chase after whoever keeps sneaking down the hallway. He is the supposed eighth person to die, hit by a marble bear clock dropped from Vera Claythorne's window.
Dr. Armstrong is an overworked surgeon who is confident but whose early career and one drunken mistake have come back to haunt him in the form of an accusation that he killed an elderly patient. Dr. Armstrong trusts Justice Wargrave, helping the judge fake his death. He is the supposed seventh person to die on the island, and goes missing, but later Vera and Lombard discover his drowned body on the rocky shoreline.
Miss Brent is a staid, religious, and sanctimonious elderly woman who uses her religion to justify being a bully, having ousted a pregnant maid who then committed suicide. She refuses to acknowledge any guilt and becomes the fifth person to die on the island, by a syringeful of poison to the neck, as she watches a bumblebee buzzing in the window.
General Macarthur is an army man who deliberately sent a young soldier who had an affair with his wife into a battle he knew would be fatal. Macarthur resigns himself to being murdered and still misses his wife, becoming the third person to die on the island, by a blow to the head with a life preserver.