Doctor: Matt Smith (Eleventh Doctor)
Companion: Jenna-Louise Coleman (Clara Oswald)
Dougray Scott – Professor Alec Palmer
Jessica Raine – Emma Grayling
Kemi-Bo Jacobs – Hila
Aidan Cook – The Crooked Man
Directed by Jamie Payne
Written by Neil Cross
Produced by Marcus Wilson
Incidental music composer Murray Gold
Series Series 7
Length 45 minutes
Originally broadcast 20 April 2013
On a dark and stormy night in November 1974, Professor Alec Palmer (Dougray Scott) and his assistant Emma Grayling (Jessica Raine) collect photographic evidence of a ghost in Caliburn House. Professor Palmer is using Emma's strong psychic powers to create a connection that appears to summon the ghost. They are surprised by the arrival of the Doctor and Clara, who claim to be from military intelligence. The Doctor shows interest in the investigation and Clara points out that the ghost appears in the same position within each photograph. Clara speaks with Emma and reassures her that Emma's feelings for Professor Palmer are reciprocated; at the same time, Emma warns Clara about the Doctor, sensing "a sliver of ice" in his heart.
The Doctor and Clara find a location in the mansion which is noticeably colder than the rest of the house, and they feel as if they are being watched. Suddenly the house grows cold and Clara feels something holding her hand when there's nothing there. The two race back to where the Professor and Emma are waiting to see Palmer's equipment activating of its own accord. A thin black disc materializes in front of them and Emma senses something crying out for help as the ghost appears in a dark hallway crying for help. The Doctor quickly takes pictures of them before the disc vanishes and the house returns to normal.
The Doctor takes Clara in the TARDIS to examine their specific location at various points during Earth's history and repeatedly takes photographs of the same area. Clara is dismayed by the Doctor's lack of compassion at witnessing the whole of humanity's history during these trips, complaining that "we're all ghosts to you". She also grumbles that she thinks that the TARDIS doesn't like her. From his pictures the Doctor comes to the conclusion that the "ghost" is actually a pioneer time traveler named Hila Tacorian. Hila was trapped in a pocket dimension where time moves more slowly; for every second she is trapped in the pocket dimension one hundred thousand years pass in the normal world. The Doctor realizes that he cannot use the TARDIS to rescue her because the entropy of the pocket dimension would drain the TARDIS of its energy within seconds. Instead, the Doctor prepares a device which includes a blue crystal from Metebelis III to stimulate Emma's psychic abilities to open a gateway to this pocket dimension. Once opened, the Doctor will travel across and rescue Hila with a harness anchored in the normal world.
Emma opens the gateway and the Doctor travels through where he finds himself on a small island of land floating in a void. He finds Hila and they are drawn to a vision of Caliburn House that Emma has generated for them as a beacon. At the same time, a creature follows them and chases them into the house. The Doctor locks the doors to slow the creature down, and Hila uses the harness to return to the normal world. The strain of keeping the gateway open causes Emma to collapse and the gateway closes, trapping the Doctor in the pocket universe. The TARDIS's cloister bell begins to sound, and Clara races to the TARDIS to find it locked. She pleads with the device via its holographic voice interface to help her save the Doctor, and after initially refusing the TARDIS finally opens up and allows Clara in. As Emma reopens the gateway again with Palmer's encouragement, the TARDIS briefly flies into the pocket universe and moves close to the ground, allowing the Doctor to jump and hang on before the creature can grab him. The Doctor and the TARDIS safely reappear in the normal world as Emma collapses from the pain and exhaustion.
Before leaving the next morning, the Doctor stops to ask Emma if she could sense anything unusual about Clara, but Emma reveals that Clara seems normal to her. The Doctor offers Hila a lift to any other place in history and concludes that she is a direct descendant of Emma and Palmer. He reasons that their relation resulted in a blood connection that helped them open the gateway to rescue her. While contemplating the bonds that love can create, the Doctor suddenly realises that there is another creature within Caliburn House. Just as Emma and Palmer were not part of a ghost story but a love story, the Doctor considers the same for the creatures — that the one trapped in the pocket universe has been trying to reunite with its mate. The Doctor asks Emma for a favour and they use Emma and the TARDIS to retrieve the other creature from the pocket universe.