Two months ago, a London car park attendant was shot dead. The officer who is investigating the murder believes it may have resulted from an armed robbery which went wrong. He is sure someone is shielding the killers. Since early February, four lorry loads of cigarettes have been hijacked in north London. On one occasion the gang was armed and so far half-a-million pounds worth of cigarettes have been stolen. As the cigarettes are sold viewers from anywhere might help solve the case.