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.
| Directing | John Baxter | Director |
| Writing | Mary Cathcart Borer | Writer |
| Writing | Geoffrey Orme | Writer |
| Production | John Baxter | Producer |
| Production | Barbara K. Emary | Associate Producer |
| Camera | Jo Jago | Director of Photography |
| Editing | Vi Burdon | Editor |
| Sound | Monica Ross | Sound |