Oakley murders rich eastern widows for their money and belongings, but things start to get a bit too hot for him, so he heads west to California, where his beloved niece Charlie lives. Pursuing him is Detective Jack Graham. At first, the niece absolutely refuses to countenance the notion that her uncle is the 'Merry Widow Murderer'. But little clues start to chip away at her faith in the man, until, after various plot twists and turns, it's not clear who is in the greater danger.