Since Frank Marker was released from Ford Open Prison at the start of this new series, some viewers have been suggesting that no man with a record would be allowed to practise as a private detective.

They are wrong. There is nothing to prevent any citizen setting up in business as a private eye. Not so long ago, in fact, two men with prison records, now working as private detectives, claimed they were better qualified than most to hold their jobs. Their argument? It takes a thief to catch one!

Frank Marker, who has always contended he was framed, anyway, runs into more trouble when he finds himself alone in his digs - but not for long.A ring at his door reveals a young woman who, for the next 36 hours, has Marker running around in circles.