Mollie and James are together and raising a family, which now consists of an older Mikey and his baby sister, Julie. Tension between the siblings arises, and as well with Mollie and James when Mollie's brother Stuart moves in. Mikey is also learning how to use the toilet for the first time.

After a single, career-minded woman is left on her own to give birth to the child of a married man, she finds a new romantic chance in a cab driver. Meanwhile, the point-of-view of the newborn baby is narrated through voice-over.

When high-powered executive Samantha LeBon hatches a scheme to spend a romantic Christmas with her new employee – the unsuspecting, blithesome James – his wife, their kids and their two dogs, Rocks and Daphne, must rescue him before he makes a terrible mistake.