'Apparently the thigh bone had been bitten clean through - with one snap of the teeth.' 'There isn't a creature on Earth capable of doing that!' After a skirmish with an alien warrior in the Middle Ages, Sarah Jane Smith's life as a journalist in Croydon seems rather tame. She decides to track down the enigmatic character who took her back in time; with the Doctor, a good story is never far away. Her intuition pays off. The Doctor and UNIT are called to investigate a grisly murder at Space World, a futuristic new theme park. Tagging along, Sarah and her new colleague Jeremy soon find themselves facing huge crab-like creatures, mind-controlling devices and vicious flesh-eating beetles. And those are just the attractions...

This is an adaptation by Barry Letts of his own radio play, in which Jon Pertwee, Elisabeth Sladen and Nicholas Courtney reprised their roles as the Doctor, Sarah, and Brigadier Lethbridge-Stewart. Barry Letts is the writer of several of the scripts for the TV series, and was producer of the show from 1970 to 1974.