Ronnie Savage escapes during transport from one prison to another, and the Ashfordly police is asked to assist Inspector Jennings from CID catching him again. They discover that Savage will be leaving the country on a trawler from Whitby and PC Rowan goes undercover at the local fish market to find out when Savage will be leaving. While he is there he finds out that the foreman Penrice has a sideline selling fish undeclared. Unfortunately Greengrass is one of his customers and he may blow Nick's cover by accident. Aunt Eileen gets a surprise visit by and old, dear friend, Antonin Clarion, who asks her to marry him and go with him back to France. And PC Rowan has passed his sergeants exam.