Hoping to avoid yet another awful family Christmas Ben pretends to be ill so Susan calls his bluff and insists on taking him to see a doctor, which results in hospital admission. Meanwhile Janey is desperate to buy Kenzo the latest 'must have' toy and the boys take advantage of Ben's absence to throw a Christmas party. Then the news arrives from the hospital - Ben really is ill and his condition requires surgery.
Susan treats Ben to a Christmas hotel break supposedly just for the two of them, but she has secretly invited other family members, including Alfie and his strange Uncle Idris and Michael's left-wing girl-friend Gwen. Abi is also working as the hotel's masseuse. Crystal, a patient besotted with Ben, arrives to say her jealous boy-friend has escaped from jail and is on his way to kill Ben. Fortunately he is caught but Ben still has to face the rest of the family, though all ends well in a room full of presents.
It's Christmas 2039. Ben looks like an octogenarian but Susan, thanks to moisturisers, still looks middle-aged. Janey has ballooned, Mikey has lost all his hair and is resorting to an ill-fitting wig and Roger, thanks to an accident at the zoo, is just a head in a glass case. Kenzo is late in arriving, giving the family time to look back on some of their worst Christmas days ever, though the worst one of all time, as Kenzo reminds them, was when Uncle Richard came to stay.
Whilst playing Santa at Susan's works Christmas party Ben becomes emotionally involved when a little girl asks him to reconcile her mother and grand-father, who have fallen out. He actually succeeds, winning rare praise from Susan for his efforts. The Harpers are less successful, though, when their lavish New year party, with fireworks, a band and food from T.V. chef Ainsley Harriott initially fails to poach guests from nasty neighbour Casey's glitzy annual event. Can recent dental patient Rolf Harris save the night with his presence or will the rocket literally go up? At least Susan and Ben see in the New Year presenting a united front.
Ben hates Christmas at the best of times but this year mother-in-law Grace is staying, Nick's hippy friend Alfie turns up from Wales and Susan insists on booking an expensive clown, Shingles, for Kenzo's birthday on Christmas Eve. To save money Ben asks Roger to play the clown but he gets drunk so Ben has to save the day. Finding an expensive ring Ben thinks it is a present from Susan - but it turns out to be from Grace for her lover - so he buys her a first edition of a Virginia Woolf novel at a grand plus.
Admiral Pellew interrupts Hornblower's wedding reception and tasks him to locate a British ship which has disappeared off the French coast, where Napoleon's troops are engaged in covert activities.