Arthur sets himself up as a 'security consultant', selling security alarms to business premises. He recruits Ron the Burglar, a reformed burglar, for his hard-won expertise, but when Ron installs a system on Arthur's lock-up, it immediately malfunctions. Arthur is unable to leave the premises and he's forced to stay there all night. A series of break-ins at premises that have installed Arthur's equipment soon arouse the suspicions of the police and Morley and Park investigate.