It's New Year's Eve in North-West London, Johnny Reeve [Karl Howman] and his friend Toby [Daniel Peacock] are out cruising, pursued by three quasi-threatening motorcyclists. At the same time, Larry [Perry Fenwick] is at Mass with his parents. Just after Mum [Kate Williams] and the Vicar [Geoffrey Drew] begin bemoaning the nuisance the motorcyclists create, Johnny and Toby pick up Larry from the church front. Through their conversations and those of other characters, we learn that the three motorcyclists are planning to throw a party at Larry's while his parents are away.
Meanwhile, at the police station gymnasium, Rebecca [Phoebe Nicholls] is sparring with Sam Diggins [Sean Chapman], both physically and verbally testing each other. After the workout, in the locker room, she teases Sam and Terry [Gary Olsen]. Out in the squad bay, the sergeant tells them they are not to break up any of the local parties, which means they can all go to Larry's party.
Larry fakes illness so he does not have to go with his parents. Toby arrives early and nearly blows it by talking about the party in front of Mum and Dad. Once the parents leave, Larry and Toby begin preparing for the guests.
The rest of the story unfolds at the party. Larry is shocked to see Sharon [Sallyanne Law] engaged to Tony [Philip Martin Brown] and keeps trying to spirit her away for a "last fling." Rebecca and Johnny keep using others to get a reaction out of each other, including Sam and Bobby [Clive Mantle]. Toby unsuccessfully tries to connect with any female. Shirley [Caroline Quentin] is so distraught by her failed attempts to connect with any guy that she plans to drown her sorrows in the bath. Sonya [Annabel Mednick] tries to win Tony back. Brenda [Kim Thomson] pursues Sam to no avail until it becomes clear that Rebecca doesn't fancy him. Terry [Gary Olsen] succeeds in getting blotto, or paralytic, as the party goes on.
Leading up to the climax, Terry and Shirley surprise everyone by sharing a moment in a full bathtub, while Bobby derisively calls Brenda a slag. When Toby defends her honor, Bobby starts to step in, but Johnny steps in from the kitchen, locks the door, and knocks Bobby out with a quick punch. With a sly wink to Toby, Johnny slips out the back. Toby seizes the moment and stages a staged fight with added sound effects so that when others burst in, he appears to have knocked Bobby out. Now seen as the hero for standing up for her, Brenda becomes the object of Toby's interest. Johnny and Rebecca finally connect. Shirley and Terry also find a connection. Larry nearly connects with Sharon until Tony interrupts, only to later break off with Sharon and return to Sonya.
In the end, the parents discover the party, and the night closes with a festive "Auld Lang Syne" performed by Chas & Dave as the group dances in a New Year's circle.
