Hungarian director Henric Hirsch, inexperienced in working for television, had difficulty coping with the cramped Lime Grove studios, out-of-order shooting sequences and William Hartnell's lack of respect for him. As a result, he collapsed during shooting of the third episode. As Verity Lambert and production assistant Timothy Combe both felt unable to run a studio, a short term replacement for Hirsch was found; Combe believes this to have been John Gorrie, who previously directed The Keys of Marinus (although Gorrie stated that he has no memory of doing so), or possibly associate producer Mervyn Pinfield. No additional director is credited on-screen. Hirsch recovered in time for the filming of episode four, with his troubles eased by the production moving to Television Centre, Combe taking on some of the director's duties and Hartnell being more considerate of his manner towards the director.
This episode survives only as a 16mm tele-recording.
Ian only appears in a pre-filmed insert in order to give William Russell a holiday during production.
This episode was thought lost until 1985, when it turned up in Cyprus, along with the first two episodes of The Reign of Terror.
This episode takes place in France in July 1794.