James Denis gives Captain Lacey a task, to deliver a mysterious package to a man with an office near the Custom House on the bank of the Thames. Lacey, who has been drawn into danger delivering items for Denis before, opens the package to find a single chess piece, a white queen.

The piece tells Lacey nothing, but he soon realizes it plays deeply into Denis's ongoing battle for control of London's underworld.

Meanwhile Lacey encounters an old army friend just returned from Antigua, who is being accused of smuggling and possibly murder. Lacey decides to help the man, whom he considers honorable, to clear his name.

But Lacey is drawn farther into the dark games of James Denis and his rival, until only his wits and memories from his past can save himself and his family from gravest danger.