It's the summer holidays and the children of Snod Hill orphanage are sent away for six weeks to stay with relations or friends of the orphanage across the country. Wally and Jeffery, two of the naughtiest boys at Snod Hill, miss the special transport provided. They are destined to spend the entire summer holidays at the sombre orphanage with the hated matron, Mrs Simebottom. Wiffybum, as the boys nickname her, is feared and not without good reason. She makes the orphans life hell during term time. She is very fond of corporal punishment and find any excuse to beat the children.

Wally and Jeffery, along with their friend, Deidrie Dimple, hatch a plan to escape the terrible clutches of Mrs Slimebottom. The decided they will build a car out of the odds and sods around the orphanage. Mr Lowery, the caretaker, helps them and soon the three youngsters are travelling south from Shropshire in the West Midlands towards Lyme Regis in Dorset.