The white whale Moby Dick is the subject of Captain Ahab's revenge. Ahab is so angry at the whale for taking his leg from him, that he will stop at nothing to get him killed. The whale has Captain Ahab so obsessed with revenge that the man cannot even sleep in his bed. That is how much the evil has taken over Ahab's life. At the end of the novel, Captain Ahab and the entire crew are killed, except for Ishmael. The evil took over them all. That shows the destruction of evil and revenge.