Maisie Williams
In the episode, the alien time traveller the Twelfth Doctor (Peter Capaldi) is lured to a hidden trap street populated by extraterrestrial refugees in the centre of London after a death sentence, in the form of a countdown tattoo, has been placed on the Doctor's friend Rigsy (Joivan Wade) by Me (Maisie Williams), the street's mayor. In an attempt to buy more time, the Doctor's companion Clara (Jenna Coleman) puts her life in danger by having the tattoo transferred to her.