Empress of Mars" is the ninth episode of the  of the British  series . It is written by  and was broadcast on 10 June 2017 on . "Empress of Mars" received generally favorable reviews from television critics.  (),  (), and  () travel to , but upon arrival, they find themselves in the middle of a conflict between the  and  soldiers. The episode marks the return of the Ice Warriors, last seen in "", an episode of the  that was also written by Gatiss.   Contents   []    Synopsis[] On  2017,  finds the words "God save the Queen" made of rocks buried under the  of . ,  and  venture to Mars in 1881 to investigate, and they discover that the planet is occupied by human soldiers from . Nardole goes back into the , but it departs for unexplained reasons, returning to the university in present day. Nardole has to ask  for help getting back. The humans have befriended an  they have named Friday. Captain Catchlove says they rescued Friday from his crashed spaceship while on patrol in Africa. In exchange, Friday allowed the soldiers to use his species' technology to travel to and mine Mars. The Doctor surmises that Friday is using them to access to his hive. They soon unearth the tomb of the Ice Queen. Despite Colonel Godsacre's order to not approach it, one guard cuts a crystal from the base of the tomb which revives the Ice Queen, Iraxxa. Iraxxa's waking leads to a confrontation with the humans. Friday tells Iraxxa it has been 5,000 years, and Mars' surface is uninhabitable; the Doctor asks Iraxxa to show mercy and gain help from the humans. Dismissing the Doctor and the soldiers, she asks Bill for her opinion, as a fellow woman. She decides to relent based on Bill's word, but then a soldier suddenly fires his rifle, the shot harmlessly glancing off Iraxxa's helmet. Provoked, she returns fire. Catchlove takes command, locking up the Doctor, Bill, and Godsacre, and traps Iraxxa and Friday within the tomb, where they start reviving more Ice Warriors. As the Ice Warriors launch their attack, Friday allies himself with the Doctor and Bill and helps the Doctor gain control of the mining device. The Doctor threatens to use it to bury all under the ice cap. Catchlove holds Iraxxa at knifepoint and attempts to force her to help him pilot a spaceship back to Earth. Godsacre manages to surprise Catchlove and kills him, then begs Iraxxa to kill him. Iraxxa calls off the attack in exchange for Godsacre pledging himself to the Ice Warriors. The Doctor covertly contacts  to assist the Ice Warriors. The Doctor and Bill help Godsacre leave the message that NASA will discover. Nardole re-appears with the TARDIS. Missy is also on board and expresses concern about the Doctor's health. Continuity[] The Doctor's  still has "no setting for wood", a defect first mentioned in "". The portrait of  displayed resembles , who played the role in "".  Outside references[] Friday is named after the character "" from 's . Bill mentions the movies  and , and the Doctor refers to the film . Upon the discovery of the Ice Empress' tomb, the Doctor says "I've got a bad feeling about this," a recurring phrase in the  franchise. Production[] The read-through for "Empress of Mars" was on 11 January 2017. Filming with the previous episode "The Lie of the Land started on 27 January, with principal shooting ending on 22 February. Writing[] The story was originally to have been set on  rather than Mars, hence the return of Alpha Centauri after 43 years.It was also reported to have originally been planned as a sequel to the ninth series episode " ", also by , referenced in the line delivered by the Ice Empress exhorting her warriors to "sleep no more". Broadcast and reception[] The episode was watched by 3.58 million overnight. It received an  of 83. Critical reception[] Professional ratings Review scores Source Rating  (Tomatometer)    (Average Score)       SFX Magazine TV Fanatic   IndieWire   8.2 New York Magazine   "Empress of Mars" received generally favorable reviews from television critics.