Nightmare (lost AVENGERS episode)

Nightmare is an episode from the lost first season of the British TV series, 'The Avengers. 'It is the episode about which the least is known; even John Cura's screenshots were lost or destroyed. The only version known to exist is the recreation by Big Finish Audio.

Background
The episode was shown live in late 1961, and its plot involves Keel impersonating the missing husband of a patient who is a famous scientist. Very little information about the making of the episode is known, but through PatricK Macnee's memoir, Blind in One Ear, we know that in the episode, Steed and Keel were chasing men disguised as MI5 agents, and this has also been incorporated into the recreation. It is also known that during the rehearsal for the attempted assassination scene in the laboratory, the prop man was able to hit the test tube that was the target accurately. However, when the scene was actually filmed, he panicked and hit the large tank instead; this sequence was also incorporated into the reconstruction of the episode. Other than this, only rumours and speculation have existed about the original version of this lost episode for nearly sixty years.