This episode was thought lost until 2004, when it was found by former BBC engineer Frank Watson.
This is the only Surviving Episode to feature the short Lived companion Katarinna.
This episode takes place on Kembel in 4000.
Features the Earliest work Of Doctor Who Alumni Nicholas Courtney, here he plays Bryt Vyon, two years later Director Douglas Camefield would remember Courtney and cast him as Colonel Lethbridge Stewart.
This episode was watched by 9.8 million viewers on its original transmission.