A distress call brings the TARDIS to the colony ship Madrigal on an important mission: transporting some of the first human colonists to their new home on Edevane’s World. But when the ship is hijacked and gets caught in a tractor beam, the computer’s AI, MAYDEN, calls on the Doctor for help.
Traveling down to the frozen planet Epiquilius, he meets the Zenbeyga, a race of creatures reminiscent of armored wombats. What could they want with the human ship and why do they want to leave the planet so urgently? And as the colonists start to wake from their cryogenic slumber, tensions flare as both sides do what they must to survive.
As the planet shakes, the Doctor soon realises there is something far worse to worry about. Something underground is stirring. And if it breaks free, it will devour the universe.