Symbols are objects, characters, figures, or colors used to represent abstract ideas or concepts.
For most of the novel, a fierce storm cuts the island off from the outside world. This storm works as a plot device, for it both prevents anyone from escaping the island and allows the murderer free rein. At the same time, the violence of the weather symbolizes the violent acts taking place on Indian Island. The storm first breaks when the men carry the corpse of General Macarthur into the dining room, symbolizing the guests’ dawning realization that a murderer is loose on the island.
When Wargrave fakes his own death and then kills himself at the end of the novel, he leaves a red gunshot wound on his forehead—first a fake wound, then a real wound. This wound, as he points out in his confession, mirrors the brand that God placed upon the forehead of Cain, the first murderer in the Bible. It symbolizes Wargrave’s self-admitted links to Cain: both are evil men and murderers.
When the characters arrive on the island, they are treated to an excellent dinner. Soon, however, they are reduced to eating cold tongue meat out of cans. At the end of the novel, both Lombard and Vera refuse to eat at all, since eating would require returning to the house and risking death. The shift from a fancy dinner to canned meat to no food at all symbolizes the larger pattern of events on the island, as the trappings of civilization gradually fall away and the characters are reduced to mere self-preservation.