A tough new sergeant, a Welshman called Raymond Craddock, arrives to take over the Ashfordly station. He is very narrow-minded and wishes to do things strictly by the book, which pits him against Ventress and Greengrass. Under their new sergeant, Mike, Bellamy and Ventress investigate the disappearance of a teenage girl called Maureen Dodds, who vanished on the night of the Valentine's disco. Meanwhile, love is in the air for Maggie and Neil.