Joan encountered the First Doctor and Susan when they were lost in the fog. She took them home for tea. Her mother seemed uncomfortable with Joan bringing people home, though she said that Joan was a "good lass".
The Doctor realised that Joan and her mother were trapped in 1943, though it was 1963 outside, and that Joan's Grandpa was the source of the trouble. When the house burned down, Joan and her mother burned too and were freed. (PROSE: Ash)