Back at the start of her imprisonment, Doctor Song becomes a guinea pig for an innovative new security system. Because it's early days for Missy, too. The Doctor is dead, and she is outraged that somebody else killed him first.
On a world where vicious beasts stalk ancient ruins, Professor Song teaches a student the finer points of archaeology. But then she meets an incarnation of the Master who is desperate to survive.
Stranded in the Vortex, a father and daughter do their best to survive, living on salvage in a ramshackle vessel. And River is caught between them, uncovering an old enemy in the most unexpected new guise.
A deep space exploration mission nears its end - when suddenly, the crew start to die. River must try to protect her colleagues and work out what else is on board their ship.