A skilled detective and his two assistants pursue a fortune in stolen jewels, tracing the theft to a passenger and the notorious criminal John Garrison Rayne. A man-overboard alarm aboard a tramp steamer reveals Rayne’s escape from confinement, while the detective moves to secure the recovered suitcase of gems and investigate shipboard conspiracies. The plot follows a methodical maritime pursuit into Porto Rico port scenes, exposing layers of theft, deception, and ruthless violence as the detective protects the loot and seeks to recapture the cunning fugitive known as the Apache.