Rival members of the underworld, jealous of "Lone Wolf" Michael Lanyard's success as a jewel thief, threaten to reveal his true identity unless he surrenders his independence and joins their "pack." Instead, Lanyard determines to quit his life of crime, only to find the way blocked by the dauntless Lucy Shannon.

Louis Joseph Vance was an American novelist, born in Washington, D. C., and educated in the preparatory department of the Brooklyn Polytechnic Institute. He wrote short stories and verse after 1901, then composed many popular novels. His character "Michael Lanyard", also known as "The Lone Wolf", was featured in eight books and 24 films between 1917 and 1949, and also appeared in radio and television series.
Vance was separated from his wife (whom he married in 1898 and by whom he had a son the next year) when he was found dead in a burnt armchair inside his New York apartment; a cigarette had ignited some benzene (used for cleaning his clothes or for his broken jaw) that he had on his body and he was intoxicated at the time. He had recently returned from the West Indies, where he gathered material for a new book. The death was ruled accidental.