As secretary and mistress of the wealthy Harris Chapman, Marian (Laraine Day) looks after his recently acquired fortune. But when Chapman falls for a new woman, cutting Marian out of his success, she decides to take her revenge. With the help of a mysterious hired gun (Edmond O'Brien), Marian develops a scheme to kill Chapman and appropriate his wealth. Hers isn't the only plot at work, however, and she soon finds herself involved in another conspiracy entirely.