Ten-year-old Nicholas is embarrassed by his Mum's pregnancy and worried about losing his status as an only child. Then - horrors! - Mum finds out she's expecting twins! Granny and Lancelot's lives are also turned upside down as they have to move out to make room for the babies. What with their house-hunting, Dad practising nappy changing and finding out - with the help of a water-filled balloon - what it's like to walk round with a bump, time goes by. Soon Mum is in labour and Dad's car won't start - luckily there's a pizza delivery van ready to come to the rescue!