Sgt. Matt Boyden is not looking forward to another night shift in Custody, but a noisy prisoner demanding food turns out to be the least of his worries. Sgt. June Ackland and PC Dale Smith bring in a drunk and disorderly vagrant who they nickname 'Olly'. Chaos sets in as a drink-driver, some cat-fighting prostitutes, an immigration officer with two deportees and two lay visitors conducting a surprise inspection arrive. As the F.M.E. takes a blood test from the drink driver, Boyden has Olly placed in a cell to rest. When the lay visitors inspect his cell, he is dead. Faced with a death in custody, Ch. Supt. Brownlow calls in CIB, and the three Sergeants on duty, Boyden, Ackland and Cryer argue amongst themselves over who was responsible. Ackland manages to find Olly's real identity, and his widow threatens to sue the Met, but June talks her out of it and discovers that his wife blames herself for his death.

As Dave Quinnan's stag night begins, an old friend turns up - Steve Loxton. A newly sober Jim Carver faces temptation and ridicule from his colleagues as the night wears on. Jenny and her friends rope DC Procter into helping them investigate a stripper who is indecently assaulting the patrons of the strip club they attend, but Vicky Hagen is forced to take matters into her own hands. Insp. Monroe waits desperately for the duty inspector to relieve him, but he is delayed for most of the night. Paranoid that the lads have hired a stripper, Quinnan takes refuge at Polly Page's flat, where she drops a bombshell that she is in love with him. Dave returns to the party, but falls on a bottle, injuring his hand. Arriving at St Hugh's, he is alarmed when his 'doctor' removes her clothes and tells him he's been a very naughty boy and will need to be punished!

Quinnan finds the body of Dennis Quigley, a man who has died of a heart attack in his car. Whilst delivering the man's personal effects to his wife, Quinnan is mortified to find they include a gift to the man's mistress, a woman named Alice. Trying to do a good deed, Quinnan resolves to deliver the gift to its intended recipient, and manages to locate Alice and give her the gift. However, things become much more complicated when his wife Jenny discovers the gift and thinks he's having an affair, while CID discover that the dead man is wanted by Interpol for diamond smuggling. Suspecting the package that Quinnan handed over may well be a shipment of uncut diamonds smuggled in from Antwerp, Cullen is left dismayed after realising the evidence has been lost.

The Section House is closing, and PC Reg Hollis is not only looking for a new place to live, he is also applying for a transfer to SO14 (the Royal Protection unit). He is about to buy a flat owned by an elderly friend, Doreen Tyler, but she changes her mind at the last minute, so he moves in with Tony Stamp temporarily. Hollis's intuition gives CID an important lead on a planned armed robbery, but his uniformed colleagues conspire to have Nick Klein organise the Section House closing party instead of him. Deciding to skip the party, Hollis goes to visit Doreen, but finds her dead in her flat. With no alibi, Hollis is the prime suspect for her murder, and he is suspended from duty. As Stamp and Klein work to find someone who can verify Hollis's whereabouts, CID discover a woman posing as Mrs Tyler's adopted daughter.