As he investigates a number of post office robberies, Nick's narrow-minded attitude towards an old enemy puts her in danger when her ex-cellmate escapes from prison and resorts to drastic lengths with her villainous boyfriend to corrupt the reformed criminal. Meanwhile, Gina is swept off her feet by a handsome Irishman who asks her to help him set up a bar in Spain, whilst Greengrass and David buy a Georgian chest after hearing that its last owner hid his valuable war medals inside it.

A convict escapes while being transferred to prison and while trying to track him, the Ashfordly officers uncover a smuggling ring in Whitby. Nick goes undercover at a fish market, while Bellamy's own tactics of finding the convict results in him being taken hostage by a gang of fugitives. Elsewhere, Greengrass enters the fish trading business, Aunt Eileen is reunited with an old flame who makes a life-changing request, while Nick receives the results of his sergeant's exam.