Ace (real name: Dorothy McShane) is a teenager from 1980s Perivale, London. She is interested in explosives, and has invented one called Nitro Nine. Whilst experimenting with it, she was caught up in a timestorm and ended up on the planet of Iceworld. In Dragonfire she met the Doctor and joined him on his travels. She has the habit of calling the Doctor "Professor" and sometimes using nicknames for other people she encounters.