She travelled with them in time to prehistoric Earth through the use of a kind of "séance" involving Block Transfer Computation. There, Mapp was harassed by sentient scorpions under Adric's control, and during the adventure she became engaged to Rupert Von Thal. She would have been stuck in that time, almost certainly to be devoured by the scorpions, but her new fiancé sacrificed himself on her behalf.
Safely returned to Victorian London, she proposed to honour Von Thal's memory by travelling broadly. She felt it would help give her writings more verisimilitude.
Mapp was reasonably wealthy, as she had a maid named Brenda. In her large Bloomsbury house across from Tavistock Square, the 500-year-old Adric winked out of existence for the last time. (AUDIO: The Boy That Time Forgot)