The Deep Blue Sea was written by Terence Rattigan in 1952, and it is now regarded as one of his masterpieces, or even his best play. This play shows a vivid and splendid portrait of the heroine Hester Collyer and her love for two men, her husband Sir William Collyer and her lover Freddie Page. The aim of this essay is to examine why she betrays her husband and lives with her lover, also why she attempts suicide, and how she finally comes to face herself and her life with the help of Mr. Miller.