Ellery Queen (George Nader) is called in by the mayor of a big city to investigate a series of murders by a killer called “The Cat” who strangles his victims with a silk cord.

Eva Gabor joins George Nader for the story of a rather loathsome heiress to a mining fortune. Many suitors seek a share of the wealth, but one by one they are murdered. The pattern points toward Eva, but Ellery finds the real motive.

Ellery is forced by a notorious smuggler, James Garvin, to accept a gift of a typewriter. Garvin is murdered and the suspects are: His daughter, his current girlfriend, his former wife, and an English diamond merchant.