Nick agrees to work on loan with CID, and is paired with old flame Jill Criddle to bring down local gangster Frank Armstrong, who has recently opened a new nightclub in Whitby. The pair go undercover as a couple at Armstrong's club. But things take a dangerous turn when Jill is kidnapped. Meanwhile, Greengrass befriends Billy Black and the pair plan to make a fortune at a horse race, but Billy is not all he seems.