Howard Foster

Professor Howard Foster, the stepfather of Peri Brown, was an archeologist. He was married to Peri's mother and his fellow archaeologist Janine Foster. (BFA: The Reaping) He already had two children of his own from a previous marriage. (TN: Shell Shock)

Whilst off the coast of Lanzarote on 9 May 1984, he found an artefact from the planet Trion and briefly met the Fifth Doctor and his companion Vislor Turlough. (DW: Planet of Fire)

Several years later in his personal timeline, the Doctor - who had regenerated into his sixth incarnation in the interim - did not remember meeting Howard, much to Peri's surprise. He attributed this lack of memory on his part to the fact that since he had met so many people during his long life, he could hardly be expected to remember each and every one of them.

Soon afterwards, Peri learned that Janine had falsely accused Howard of being at least partially responsible for her sudden disappearance from Lanzarote on the day that he found the artefact, which led to the collapse of their marriage by September 1984. (BFA: The Reaping)

Behind the scenes
According to one account, he sexually abused Peri, an act for which she never forgave him. (TN: Shell Shock) However, this is contradicted by the intent of the actors and director, as relayed on the DVD commentary. It's also narratively contradicted by BFA: The Reaping and CC: Peri and the Piscon Paradox. Both reveal much about Peri's early family life. The Reaping indicates the reason her mother divorced Howard had nothing to do with any abuse of Peri. Had Peri been abused by Howard, that surely would have been the central cause of divorce. In Piscon, Peri relates another instance of abuse, this one from her first major boyfriend. Had she been also abused by her step-father, it is likely she would have related that, too.