John Neville stars as R. Austin Freeman’s brilliant forensic expert Dr. John Thorndyke. A girl has been found with her throat cut in an East End lodging house. Thorndyke and his partner, Dr. Jervis, examine the body and find a clue which the police completely overlook.

A young post office clerk is gunned down at her counter in a violent robbery. Private detective Max Carrados (Robert Stephens) has vital evidence in the case. But a blind man is an easy target to a gang of desperate men.

Peter Vaughan stars as Arthur Morrison’s notorious villain, private inquiry agent Horace Dorrington. In this story of fraud and industrial espionage, the deadly rivalry of two big bicycle companies leads to some very dirty work at the race track and at the stock exchange.

Every jewel thief in the country has got his eye on the fabulous Wiltshire Diamonds, two hundred perfectly matched stones. To help safeguard the jewels, the Duke calls in man-about-town Simon Carne (Roy Dotrice), a rich and charming hunchback with a mysterious side, whose wit and sophistication make him irresistible to women.

Donald Pleasence plays world-famous ghost hunter Carnacki, called to Higgins Hall to investigate supernatural threats against the bride-to-be. The family ghost is an invisible horse which, in the past, always caused the death of the daughter of the house on the eve of her wedding.

Diamond merchant Leon Bouvier possesses the Mirror of Portugal, but his brother Jacques believes it should be his. Jacques arranges for private agent Horace Dorrington (Peter Vaughan) to steal it, but Dorrington wants the diamond for himself. After Leon is robbed, he calls in Dorrington himself to investigate the case.