Adam is devastated when he is diagnosed with testicular cancer and a probable malignant tumour. Jenny throws Pete out of the house following his infidelity, telling him to take all of his things with him. Unable to cope with their petty fighting, Adam blurts out that he has cancer, shocking the couple. David's younger brother, Nick (Stephen Moyer), arrives at the Marsdens' house and takes a liking to Rachel. After his surgery, Adam and Rachel get back together, and Pete and Jenny give their marriage another try.

David arranges a trip for the couples to Lindisfarne, where they can see in the new millennium together. Pete and Jenny's relationship is frosty but Adam and Rachel make up for lost time in the bedroom. After Adam and Pete temoporarily get stranded in their boat while coming back from the mainland, the Giffords' relationship gets worse. Karen tells David she is pregnant. After Ramona removes the batteries from Pete's "Millennium clock", the couples see in the year 2000 on the beach.

Pete and Jenny have separated, so he has been living at Adam and Rachel's. He moves back in with Jenny as her lodger when Adam and Rachel tire of his uncleanliness. As Karen and David return home with their new baby twins, Ellie and Olivia, Heather, Karen's ex-pat mother, arrives from Spain. At a dinner party, she takes a liking to Felix, one of David's clients. Jenny has also been invited, and is smitten with Robert, another client. Pete prepares breakfast for Jenny on their anniversary but is saddened when she receives flowers from Robert. Rachel tells Adam that her period is late.