Parts: 1 (45-minute)
Writer: Rona Munro
Airdate: 17 June 2017
Production Code: n/a

Doctor: twelfth
Companions: Bill, Nardole

Megalomaniac of the Week: Missy
Creature Feature: Eaters of Light

Story: Bill cajoles the Doctor into bringing her to Roman-occupied Aberdeen in the second century AD, where she plans to prove to him that the mysterious disappearance of the Roman Ninth Legion was merely the result of a voluntary troop relocation. The Doctor, who has personally lived in Roman times, is dubious — he still believes some calamity befell them — but allows Bill to go off on her own to search for them.

While the Doctor and Nardole stumble across local Pictish civilization, Bill does indeed find a remnant of the Ninth Legion... in the form of a lone soldier, trapped at the bottom of a pit, wracked with guilt and fear. As he soon tells Bill, the Ninth Legion was indeed nearby until recently... but their entire force has been decimated by a bloodthirsty monster, which still lurks in the woods outside...