The Mummy Strikes

Following from Clara's admission that she does not want to see The Doctor again after the events that took place in "Kill the Moon", several weeks have passed, and Clara has realised that her feelings of hatred towards The Doctor are no more and so allows him to take her on one last trip in the TARDIS. He therefore takes her to a space-bound recreation of the Orient Express with passengers dressed in period pieces.

However, aboard the train, they find that an elderly woman, Mrs. Pitt, has recently died, claiming that she was attacked by a mummy that no one else could see. They retire to separate cabins for the evening, where Clara calls Danny Pink and gets advice on how to deal with her relationship with The Doctor, and then later, encounters Maisie, Mrs. Pitt's granddaughter, who is distraught over her relation's death and frustrated with the inability to see her body. Clara tries to help but the two of them get trapped in the luggage car, where the mummy's sarcophagus sits, and the two bond while waiting for help.

Meanwhile, The Doctor has started to investigate Mrs Pitt's murder, meeting the train's engineer Perkins who is also curious as to her death. The Doctor also speaks to Professor Moorhouse, who explains about the mummy that is being transported on the train, and the myth about The Foretold including the saying: 'Those who bear The Foretold's stare have 66 seconds to live'. As they talk another death occurs when the train's chef dies in a similar manner as Mrs. Pitt.

The First Victim

The Doctor then discovers Clara's situation but when he tries to rescue her, the lights flicker, the sarcophagus opens and the countdown starts. But before he can gain entry to the locked part of the train, where Clara and Maisie are trapped, Captain Quell and his men take him as a prisoner for falsifying his credentials. When the 66 seconds are up, they find that a guard aboard the train has been killed instead of Clara or Maisie.

The Doctor begins to question what is really happening on the train, recognising that most of the passengers are scientific experts and demands to know why. As soon as The Doctor mentions this the train suddenly stops in space, and the illusion of the original Orient Express and several of the passengers dispersed, revealing that they are in a laboratory. The train's computer, Gus, tells them they are now ready to study the force behind the attacks so that they can reverse engineer whatever power it has.

Aboard the Orient Express

It is not long before another death occurs. This time it is Professor Moorhouse who manages to stammer out a few details about The Foretold before he is killed. The Doctor contacts Clara, who informs him that she has discovered an inventory of previously lost ships and their crews that reveals that the sarcophagus is meant as a containment unit for whatever the force is, and that this is not the first attempt by whoever is controlling events to discover the nature of The Foretold. Because The Doctor is discovering to much, about the previously failed attempts to defeat The Foretold, Gus forces The Doctor to end the call and return to work by expelling all the air from the kitchen car, killing the kitchen staff and threatening to kill more.

The Doctor, with the help of Perkins, discovers that the past victims were all suffering from various conditions, and that The Foretold is targeting the weakest. Captain Quell reveals he suffers from post-traumatic stress disorder and soon sees The Foretold. Before he dies he is able to provide enough information to The Doctor to help him identify that The Foretold drains the victim's energy through phase shifting. Perkins identifies the next likely victim, Maisie, due to her recent trauma, and The Doctor tells Clara to bring her to the lab, having Gus unlock the storage door.

On the way there, Clara sees that the TARDIS is protected by a force field, and when she tells The Doctor about this, she realises that Gus must know about The Doctor to prevent access to the TARDIS. The Doctor is forced to admit that Gus had been trying to bring him here to help for some time. On discovering this an angry Clara accuses The Doctor of taking her into a dangerous situation again.

Masie

At this point, Maisie sees the mummy, and The Doctor absorbs some of her memories as to be able to trick The Foretold into thinking he is the victim and not her. Within the 66 seconds, The Doctor is able to discover that The Foretold is a former soldier from a war thousands of centuries ago, having been modified with phase-shifting camouflage to be an assassin. With less than a second to go before The Foretold kills The Doctor he correctly deduces that if he surrenders it will stop its attack. This it does and so it manifests itself before everyone. It then salutes The Doctor before disintegrating into dust, leaving its phase-shifting device behind.

Gus then congratulates the passengers on the success before beginning to evacuate all the air aboard the train. With everyone, including Clara, passing out due the lack of oxygen The Doctor manages to rewire the phase-shifting device, taken from The Foretold, and convert it into a short-range teleporter, rescuing all the remaining passengers on the train to his TARDIS just before the train blows up - the explosion having been caused by Gus so that no evidence could be discovered.

Clara wakes up, on a rocky beach, and The Doctor explains to her what had happened and that he has dropped everyone he had rescued onto the nearest planet. The Doctor then enters the TARDIS where Perkins tells The Doctor that he has fixed one of the power couplets but two of the drive stacks need replacing. The Doctor offers Perkins a job, to maintain the time machine, but Perkins politely refuses.

As Perkins leaves Clara enters the TARDIS and, reflecting back on their previous conversation, asks The Doctor if he loves being the man who has to make the impossible choices all the time. The Doctor responds that it is his life. Then Clara's mobile phone rings. It is Danny back on Earth who is expecting that she will finally end her trips with The Doctor. But instead when she ends the call Clara decides to forgive The Doctor and so announces to him that she is ready to continue her travels in the TARDIS as she wants to visit more planets. Surprised by her sudden change of heart the delighted Doctor excitedly tells her about 'one that's made entirely of shrubs' and plots a course for it.