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.
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.
