Teenager Cassie Booth disappears whilst on her paper round and her clothes are found in a boat house belonging to Karl Wilding, a business with an alcoholic wife Rebecca. Wilding is the prime suspect but then seemingly helpful Stephen Warrington, a wine merchant who has initially brought a complaint about a house being used as a brothel, demonstrates too much interest in both the case and in Pat North, now living with Walker as his partner. Warrington is a man with bipolar disease who suffers from frightening mood swings - as Pat will discover.
With all niceties gone now and Walker too self-absorbed to realise the peril that his girlfriend is in, Pat North is abducted by Warrington and forced to discover Cassie North's corpse. He is eventually brought to trial in what should be a very simple matter but it is apparent that Karl Wilding also had a part to play in Cassie's murder.