Kathryn McDonnell was captain of the S.S. Pentallian. Kathryn's ship collected energy from a sun, unaware that it was actually a living being and that removal of the energy caused it great pain. The life form, angry with them for mining its heart, pulled the ship towards its surface and began killing the crew. It possessed McDonnell's husband, Korwin, soon followed by Dev Ashton. McDonnell sacrificed herself to save her crew by opening an airlock and sending her husband and herself falling into the sun.

_{Biography from the TARDIS Data Core article, licensed under CC-BY-SA}