Lisa Foster was a pupil in Clara Oswald's class at Coal Hill School. She was also the daughter of Paul and Hannah Foster, and the older sister of Molly Foster.
Biography
When the Twelfth Doctor detected reality distortion energy around Lisa's home, he took Lisa and Clara there to investigate. On seeing that her front door was left open when it was usually closed, Lisa ran inside.
In the garden she was attacked by a Fracture possessing the body of a human. To her surprise, her father appeared and bargained for her life. Her father had died in a car crash a year previously, but the following year a version of her father travelled through the Void from an alternate Earth and reached their universe. This version of Paul had survived the car crash, but lost his wife and daughters.
After Clara freed Lisa from the Fracture and the Doctor helped family escape they all holed up in Clara's apartment. The Fractures soon discovered them there, and so they fled to the UNIT HQ at the Tower of London. When the Doctor reopened the Void, pulling the Fractures back inside, he decided to let the alternate Earth version of Paul stay with his family in their own universe, knowing that he himself would be a bigger target for the Fractures than Paul would. (COMIC: The Fractures [+]Loading...["The Fractures (comic story)"])
Other realities
In a parallel universe, it was Lisa, Molly and their mother Hannah who died in the car crash, and Paul Foster who survived. (COMIC: The Fractures [+]Loading...["The Fractures (comic story)"])