David and Monty are two friends of Susan and Betty Potter whose father runs a fleet of lorries. One by one, his lorries are involved in accidents and sabotage is suspected. The children are determined to find the culprits.

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Main Cast: Douglas Barr, Ivor Bowyer, Angela Glynne, Angela Fouldes, David Hannaford, John Longden, Carole Ann Ford

Director: John Baxter

Writers: Mary Cathcart Borer, Geoffrey Orme

Editor: Vi Burdon

Cinematographer: Jo Jago

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