A petty crook finds himself mistaken for a murderer and a secret agent.

Operation Third Form, features a fresh-faced John Moulder-Brown (Deep End) in a sparkling performance as the schoolboy out to foil a pair of north London crooks, is a pacey boy's own adventure complete with a groovy 1960s soundtrack.

A group of young railway enthusiasts attempt to stop the closure of the local railway by trying to raise money to buy it and the steam engine "Matilda." They get help from a pair of men claiming to be enthusiasts but who turn out to be robbers who plan to hold up the mail train

A vicious gang of crooks plan to steal the wages of a local factory, but their carefully laid plans go wrong, when the factory employs an armoured van to carry the cash. The gang still go ahead with the robbery, but when the driver of the armoured van is killed in the raid, his wife plans revenge, and with the police closing in, the gang start to turn on each other.