Sarah Brown was one of the wives of Iziah Brown.
Sarah was a paleontologist. She met the Fifth Doctor, when he visited Eternity, California. He was pretending to be Dr Sebastian Rowley, who had written "On the World of Our Pre-history", and she was thrilled to meet him.
After the Master had put the Doctor in a cell, Sarah used explosives to help him escape. However, they were confronted by the Master and several hypnotised townspeople. The Master killed Sarah, in the process gloating that he had wiped out Peri Brown from existence. (PROSE: A Town Called Eternity)