Three young children live on a remote farm in the North of England; their mother is dead and their father is too busy to look after them. Kathy (Hayley Mills) is the eldest, Nan (Diane Holgate) is the quiet child of the family, while six year old Charles (Alan Barnes) is the most outspoken.

The children wage constant guerrilla warfare against farmhand Eddie and the traps he sets for wild animals. They rescue three kittens that Eddie believes he has drowned. Charles tries to give his kitten to the Salvation Army who tell him that Jesus will look after the kitten. They put the kittens in a barn and when returning that night to see if they are safe, Kathy stumbles on an unshaven man (Alan Bates) taking refuge. Asked who he is, the man replies in shock "Jesus Christ!" and so begins a comical and touching series of events with the three children believing him to be the Messiah. He is in fact a murderer on the run...