The Doctor: Jodie Whittaker
Susan Lynch – Angstrom
Shaun Dooley – Epzo
Art Malik – Ilin
Ian Gelder – Voice of the Remnants
After arriving in deep space by mistake, the Doctor and her friends are rescued by Angstrom and Epzo, two humanoid pilots competing in a large intergalactic race. Reaching the dead, yet hostile planet of Desolation, slightly removed from its gravity field, the group and pilots meet with the race's organiser Ilin, using a long-distance hologram. Both pilots learn that the race's final event involves reaching an object referred to as the Ghost Monument for extraction before the planet completes a single rotation. A curious Doctor learns from Ilin's data that it is the TARDIS, stuck in mid-phasing due to the damage it suffered. Joining the pilots in their race, the Doctor promises to get her new friends home once they have reached the finish line.
The group and the pilots locate and repair a solar-powered boat, using it to reach the ruins of a former civilisation that is now inhabited by sniper robots. The Doctor uses the remains of one robot to temporarily disable the others with an electromagnetic pulse, locating a series of tunnels the ground can use as a shortcut to the finish line. During this time, the Doctor learns that Angstrom seeks the cash prize to save her family from ethnic cleansing by the Stenza, while Epzo is out for himself due to his upbringing to distrust others. Uncovering Desolation's history in the tunnels, the group learn that the residents died from creating weapons of mass destruction for the Stenza, with the dead cleared up by cloth-like creatures called the Remnants. Trapped by a group of Remnants when forced to a gas-ridden area on the surface, the Doctor destroys them with Epzo's self-lighting cigar igniting the gas.
Reaching the monument's location, the Doctor convinces the pilots to claim joint victory in Ilin's holographic tent. Ilin reluctantly agrees to this, but refuses to teleport the Doctor and her friends off the planet with the pilots. A despondent Doctor apologises to her friends for stranding them, but pauses when she hears the TARDIS emerging, using her sonic screwdriver to fully materialise it. With her ship returned, finding that it changed itself both externally and internally in her absence, the Doctor offers her friends a trip home as she promised.