The Doctor and Belinda

Still unable to return to Earth on the 24th May 2025, The Doctor and Belinda Chandra are still stranded. The Doctor pilots the TARDIS to a spaceship that is 500,000 years into the future. As they step outside, they find themselves amongst a squad of troopers under the command of Shaya Costallion, who immediately draft them into an orbital drop onto a stark, barren planet.

Upon reaching the surface The Doctor uses the Vindicator to take another reading in his attempt to return Belinda to Earth in 2025. After doing so they find themselves back with the squad of troops. They discover that the group are investigating the lack of contact from a mining colony. Inside the colony, a grim scene unfolds: all the miners have been brutally murdered, save for one survivor, Aliss Fenly, a deaf cook. Strikingly, every mirror in the colony lies shattered. Aliss recounts a horrifying tale, claiming the colonists descended into madness, ultimately killing one another. She also reveals that she too was forced to became a murderer when her own friend went mad and turned hostile. But she insists that this was purely in self-defence.

While Belinda and most of the troopers stay to support Aliss, The Doctor accompanies Shaya to the colony’s control centre. There, they discover a massive well that served as the focal point of the mining activities. Separately, both The Doctor and Belinda uncover the unsettling truth: Aliss and the troopers have no knowledge of Earth or humanity.

The Doctor Exits the TARDIS

The Doctor watches back the last video recorded by the colonists, and uncovers a chilling implication - that something had emerged from the well. When queried, Shaya discloses that the planet was once named Midnight. The moment The Doctor hears this, he realises that the dark force responsible for the miners’ demise is the same entity he faced during a previous visit to this planet 400,000 years ago (see "Midnight").

Meanwhile, as the tension escalates Belinda briefly catches a fleeting glimpse of something sinister lurking behind Aliss, but none of the group can see anything on further investigation. However, when a trooper moves behind Aliss, catastrophe strikes when the trooper is violenty thrown across the room to her death.

On Planet 6-7-6-7

When The Doctor and Shaya return to the group, Belinda theorises that an unseen entity lurks behind Aliss and it will kill anyone who moves behind her. Aliss corroborates this theory, explaining that the entity will transfer its influence to anyone who kills her.

Trooper Cassio, frustrated by Shaya's lack of action, relieves her of command, believing decisive action is needed. In a reckless attempt to bring the entity out into the open Cassio moves behind Aliss to attack the entity. But when Aliss turns to face Cassio, chaos ensues as multiple troopers are killed when they find themselves behind her back. Shaya eventually regains authority and smartly instructs Aliss to turn around, resulting in Cassio's demise.

The Doctor, seeking a connection with the entity, attempts to communicate, and an unspoken understanding passes between them. He deduces that the entity whispers to its host in a frequency that Aliss, due to being deaf cannot hear, thus ensuring her survival. Convinced that the entity fears its own reflection, The Doctor ingeniously creates a makeshift liquid mirror by causing a leak of refined mercury behind Aliss. This forces the entity to confront itself, ultimately liberating Aliss from its influence.

Inside the Mining Colony

The group then make a desperate bid to flee the colony. Aliss and two troopers leave first, though unnoticed by the others the airlock shows four life signs. Just as they prepare to follow The Doctor, Belinda, Shaya, and trooper Mo Gilliben realise that the entity is lurking behind Belinda. In a split second, Shaya makes a precise shot, hitting Belinda in a way that allows her to be revived later. The entity then seems to transfer to Shaya, who heroically sacrifices herself by racing through the colony, before plunging into the well, so giving the others a chance to escape.

Back in the TARDIS, The Doctor and the revived Belinda both share their concern that the Earth is unknown in this future. Meanwhile, aboard the mothership, Mo reports the mission's events to Mrs. Flood, detailing The Doctor's order to have the planet nuked from orbit. Mrs. Flood is pleased to hear that The Doctor is utilising a specific device, called a vindicator, in an attempt to return to Earth.

In a corridor, Mo and another trooper respond to the sound of the TARDIS dematerialising. When they find nothing, Mo notices the other trooper looking over her shoulder, her expression turning fearful, implying that the entity might have escaped by using Mo as a host.