A bachelor and his quick-witted companion surprise a burglar in their library and discover a tiny black star that ties the intruder to a notorious thief who taunts the police. Their capture of the man pulls them into a prolonged pursuit that unfolds through clever deceptions, daring thefts, bank-vault plots, society intrigues and narrow escapes. Clues, disguises and police maneuvers interweave as the chase moves from quiet rooms to public events and culminates in a tense confrontation that resolves the case and places the criminal in custody.