Marius' nurse was a member of the staff at the Bi-Al Foundation who, along with Parsons, helped examined the Fourth Doctor when he was infected with the Nucleus. Working with Frederick Marius and Parsons, she scanned the Doctor and Leela for a possible antidote to the Virus.
She went to help with the victims of a shuttle crash only to find the crew were possessed by the Virus. When she and the rest of the group returned to the isolation section, they found it under attack from Lowe and other possessed individuals. She assisted with the plan to clone the Doctor and Leela and inject the miniaturised clones into the Doctor's body. Marius hid the nurse in the cloning cubicle shortly before Lowe and his men burst in, killing Parsons and infecting Marius. The nurse managed to slip out of the room, staying to watch Lowe be cloned as well before going to alert Leela and K9. (TV: The Invisible Enemy)