Crystal was a singer at the Number 10 nightclub in Clarendon Square. She had played in Europe but never London. At the club, she performed the song "Strange Attractor". She first met the Doctor and his companion Jason, a French aristocrat from 1789, when they stopped the Cybermen from kidnapping a US Envoy from her nightclub. She subsequently helped them stop a plot by the Cybermen and the Dalek Emperor. Crystal and Jason soon fell in love. She sang "Sky High" with Jason, then returned to the club, but decided to join Jason and a third companion, Zog, in the TARDIS. (AUDIO: The Ultimate Adventure)