New companion Bill Potts has joined the Twelfth Doctor on a brand-new adventure, taking them to an island in the Atlantic in the 9th century CE. Caught in the middle of a stand-off between a group of Vikings and Ice Warriors, Bill and the Doctor had to ensure the mighty battling forces united against an even greater threat – a sentient disease-carrying Flood!

But who is responsible for all of this? The Doctor has a hunch, and it can only bring more devastation if he’s right…