After pulling off a small train robbery, “Little” Walter (Ronald Fraser) and his gang hide out in a deserted monastery on a remote Cornish island.
There are six of them. The rotund Walt; his blonde girlfriend Bikini (Barbara Windsor); pint-size Willy (Melvyn Hayes), a poet and thinker; Squirts (Bernard Cribbins), a greyhound-obsessed gambler; Specs (Davy Kaye), a nightclub habituée of small stature; and Lorenzo (Grégoire Aslan), a tall Spaniard.
Disguised as monks, they slowly adjust to their new contemplative life of tending animals and crops, surviving the added tribulations of visits by a group of tourists and some authentic monks.
Visiting the mainland, Walt and Willy come across a crabby old fisherman called Phineas (Wilfrid Brambell). Realising he will do anything for a few shillings, Walt gets Phineas to join the gang as a go-between for handling stolen goods with the aid of his boat.
Phineas has a granddaughter called June (Francesca Annis) who is so attractive that Willy almost forgets his masquerade, and he begins to feel like a wolf in monk’s clothing.
Meanwhile back at the monastery, this new pastoral existence soon turns out to be much to the gangs liking – much to their surprise – with a return to a life of crime seemingly less appealing by the day.
Gradually, the clean, fresh life in monastic surroundings has a good influence over Walt and his gang. They till the land, milk the cows, feed the chickens and plant vegetables. They even plan to leave their cloisters and return to London to live a law-abiding life.
But on the mainland, the local constabulary are put on the scent when Brother Squirts starts laying very big money on greyhounds through the local bookmaker and their cover is ultimately blown.