ratings The episode was broadcast on BBC1 on 9 October 1965. Viewership dropped from the preceding serial, while the Appreciation Index remained reasonable at 54. 16 mm film recordings were made available for international sale, but the episode was never sold overseas, and BBC Enterprises withdrew it in 1974. The Australian Broadcasting Corporation considered the recording, but it was rejected by the Film Censorship Board in September 1966 as it was considered to constitute "horror", particularly the masked aliens, Varga mutations, and dialogue about murder. The original 405-line tape was cleared for wiping in July 1969, and the episode was erased in July 1974. It remains missing; no known footage exists, though an off-air audio recording was made by fan David Butler. Critical response Bill Edmund of Television Today described the episode as an "exciting start" to The Daleks' Master Plan. Several viewers were confused by the lack of Daleks in the following serial, and some felt that they had become less frightening; conversely, some felt that the episode's other monsters were too scary. In A Voyage Through 25 Years of Doctor Who (1988), Ian Levine praised the "array of creatures", particularly the design of Malpha. In The Discontinuity Guide (1995), Paul Cornell, Martin Day, and Keith Topping described the episode as "macho, with a sinister atmosphere". In The Television Companion (1998), David J. Howe and Stephen James Walker wrote that the presence of the lead actors was "hardly missed" due to Nation's script and Martinus's direction, praising the tense atmosphere and set designs. Commercial releases The story was novelised as part of The Daleks' Master Plan Part I: Mission to the Unknown by John Peel with a cover by Alister Pearson, published in paperback by Target Books and W. H. Allen in September 1989. An unabridged reading of the book was published as Daleks: Mission to the Unknown by BBC Audiobooks in May 2010 as a five-disc set, read by Peter Purves and Jean Marsh with Dalek voices by Nicholas Briggs. Audio from the episode featured on the first CD of the five-disc soundtrack The Daleks' Master Plan, released by BBC Worldwide in October 2001 with linking narration by Purves; the first CD was distributed with the magazine SFX to promote the full set. In April 2010, The Telegraph printed vouchers for readers to obtain the CD from WHSmith. A library edition of the audiobook was released by AudioGO