In the episode, an entity called the Great Intelligence (Richard E. Grant) kidnaps Victorian-era Paternoster Gang detectives Madame Vastra (Neve McIntosh), Jenny Flint (Catrin Stewart), and their butler Strax (Dan Starkey), to force their friend, time-travelling alien the Doctor (Matt Smith), to go to the planet Trenzalore, the site of the Doctor's future grave.

In 1893, Madame Vastra and Jenny Flint are given information concerning the Doctor by Clarence DeMarco, in return for a stay on his execution.

They use soporific drugs to hold a conference call through time and space between themselves, Strax, River Song, and Clara, in a dream.

During their conference, eyeless humanoids called Whisper Men kidnap Vastra and Strax and kill Jenny.

The Doctor and Clara travel to Trenzalore, the planet holding his future grave, to save his friends.

The planet is covered with tombstones, the result of a great war, while a future version of the TARDIS (having deteriorated and grown to enormous size) stands above the graveyard.

An echo of River, still telepathically linked to Clara, helps direct the two to an escape route that leads to the giant TARDIS.

The Great Intelligence enters it in order to undo the Doctor's past as revenge for all the defeats it has been dealt.

She enters the time stream to restore the Doctor's timeline, bringing Jenny and Strax back in the process.

Echoes of Clara fall through space and time and appear in adventures of the Doctor's previous incarnations.

Moffat wished to create a more funeral-like atmosphere, akin to that which appeared in the episode Logopolis (1981) which depicted the Fourth Doctor's regeneration.

Clara would additionally have referenced seeing Amy Pond falling out of the Pandorica (as depicted in the 2010 episode "The Big Bang") and the Doctor's death at Lake Silencio (depicted on-screen in the 2011 episode "The Impossible Astronaut"), which would have had her face overlaid on top of crew members who had accidentally entered the shots of both scenes, with Moffat attempting to retcon both crew members as being splinters of Clara.

Stunt doubles were used for some other brief appearances, including the Sixth Doctor walking past Clara while she is in a corridor.

Eve de Leon Allen and Kassius Carey Johnson additionally reprised their roles as Angie and Artie, two children Clara looks after, in the episode.

Additional roles include Sophie Downham as the young Clara and Paul Kasey, who portrayed the Whisper Men.

[22] Moffat later complimented the "210 of them, with the top secret episode in their grasp – and because we asked nicely, they didn't breathe a word.

[25] When viewers who watched the episode later on were taken into account, the figure rose to 7.45 million, making Doctor Who the third most-watched programme of the week on BBC One.

However, he also noted that the episode had "a tad too much clunking exposition, the odd spot of creaky CGI and some unconvincing metaphors about soufflés and leaves."

[33] Patrick Mulkern of Radio Times praised the episode, highlighting the performances of the cast, the direction of Metzstein as director, and the reveal of John Hurt as the War Doctor.