In the serial, the Doctor and his travelling companion Romana (Lalla Ward) seek to free the time-sensitive Tharils from a group of slavers led by Captain Rorvik (Clifford Rose).
Rorvik's crew realise that the null space is shrinking as the distances between the gateway, the TARDIS, and slaver ship continue to decrease.
While the Doctor warns that this action will be as doomed as the previous ones, Romana regroups with Lazlo and Adric, and together they free the remaining Tharils on the slaver ship.
As the saved Tharils pass through the mirror, Romana announces that she will be staying with them, having become empathetic to their plight and not wanting to return to Gallifrey.
The story was influenced by a radio serial he had done in 1979 called "The Babylon Run" as well as the films of Jean Cocteau, such as Orphée (1950), in which mirrors provide a gateway into another world.
[2] Ward and Baker were in a relationship and had been for some time, but by now things were turning acrimonious between the two, with many production personnel believing that they were on the point of splitting-up.
[3] Joyce was keen to push the limits of the series by directing the serial like a film as he considered some of the earlier productions to be quite bland and workmanlike.
[4] This approach however caused problems early on with significant delays in order to achieve various shots such as the pan through the spaceship in the opening sequence.
[4] In the end, the serial was completed and was indeed a departure in terms of style over the norm and was complimented by Bidmead, but Joyce was never to work on Doctor Who again.
[6] Ratings for the series increased with Warriors' Gate compared to the previous four serials of the season, due to the fact that the rival ITV network were no longer scheduling Buck Rogers in the 25th Century against Doctor Who.
Paul Cornell, Martin Day, and Keith Topping wrote of the serial in The Doctor Who Discontinuity Guide (2013), praising the direction and Romana's departure from the series.
"[9] A novelisation of this serial, written by Stephen Gallagher under the pseudonym "John Lydecker",[10] was published by Target Books in April 1982.
It and Terminus (Gallagher's other novelisation of his own script under the John Lydecker byline) are the only two Target novels that consist of continuous prose with no chapters.
The novelisation contains many elements abandoned during the story's production, including the slaver's opening pursuit and damage at the hands of an Antonine Killer craft.
This serial was also released as part of the Doctor Who DVD Files (issue 87) in May 2012, and The Collection - Season 18 Blu-ray boxed set in March 2019.