Toos worked aboard the control deck, with one of her roles being to identify rich veins of ore. After Chub was murdered, Toos and the other crew members were gathered together by Commander Uvanov to discuss the situation. Toos was dissuaded by Dask from following Borg and Cass to actively search for the Fourth Doctor and Leela, who were suspected of the murder given that they were an unknown quantity. When they were captured, Toos agreed that the Doctor's claims that he was not responsible were plausible given that "as a lie [it was] pretty feeble".
Returning to work, Toos reported that they were nearly fifty percent under target to meet the quota of ore assigned to them. She suspected that without a rich vein they would return with the miner half empty. Toos was on the control deck when the motors were jammed. Chief Mover Poul contacted her for a report and asked her to told the vehicle steady, receiving a sarcastic remark in reply. The Doctor and Leela, having been freed from their bonds, went to the control deck and the Time Lord advised Toos to "cut the power". The readings increased until they were 85% above safety. The Doctor had Dask cut the zeta links, saving the sandminer as the levels returned to safety.
SV7 contacted Toos to confirm an order given to it by Poul - to restrain Commander Uvanov - and she corroborated it. Toos further requested the SV7, who now addressed her as Commander, perform a full scale mine integrity survey. As she was visibly in pain, Leela pulled back Toos' sleeve to reveal a wound on her wrist. She claimed she hadn't mentioned it as there was "too much to do". Leela bound the wound for her, telling her the old Sevateem saying, "If you're bleeding, look for a man with scars".
Toos asked Poul to explain why Uvanov was under guard and he explained that he believed the former Commander to be the murderer, telling Toos a story about how he had left a man to die on a previous expedition. She was initially sceptical, given that an enquiry would have followed, but Poul explained that he had avoided it as he produced results being "the best pilot" the company had.
Retiring to her cabin, Toos rested on her bed. She was woken when SV7 entered to report that Uvanov had escaped his guard by ordering it away. Toos asked why his voice had not been removed from the command program, to which it replied that no order in that kind had been given. She assented to SV7's offer of a status report and it informed her that repairs were progressing but there had been localised failures in the power system resulting in "door and light malfunctions".
After SV7 left, the Doctor contacted Toos to warn her that the Sandminer robots were responsible for the killings. She was reluctant to believe such as thing possible, but agreed to round up the others and bring them to the control deck. However, when she opened her cabin door, she found V6 on the other side. After it disregarded her order to return to its duties, she closed the door, trapping its hand. Toos struck its hand, which V6 de-attached from its arm.
It gained access and, despite her pleas, began chocking her. She was saved when SV7 contacted V6, ordering it to move to section J. As this was a priority call, it released Toos and left. D84 found her, and Leela came along shortly after, with the latter comforting Toos by holding her.
Leela assisted Toos to walk towards the control deck. On the way, they hid inside a hopper. The acting Commander contacted SV7, unaware of its conversion to Taren Capel's creed, and was asked to report her location. Leela convinced her to lie, and she told it she was in her cabin. Toos remarked that SV7 had failed to identify her voice, which was unusual given it was in the command program. Leela explained this as proof the Super-Voc had been tampered with. They arrived upon the control deck and Toos told the Doctor she accepted his claim of a "robot revolution". Uvanov was also on deck, resuming his role as Commander and explaining to the group the circumstances of his supposed murder, as reported by Poul, where the victim had been a sufferer of robophobia who had run into trouble.
The Doctor enquired if blasting powder was kept aboard the sandminer and Toos replied that "half a dozen z-9 electron packs" were available. The Time Lord explained that, by passing "a positive charge through the metal plate, you'd be able to magnetise them and have anti-robot bombs". The Doctor and Leela left Toos and Uvanov on the deck to produce these weapons. When Dask, who was in fact Taren Capel, pleaded with them through the door to let him in, Uvanov moved to do so, put Toos blocked his way and persuaded him otherwise. They finished crafting the bombs and used one to destroy V5.
Toos and Uvanov left the deck and moved through the sandminer. They evaded SV7 by hiding behind an art piece but encountered it again after it had killed Capel, not recognising his commanding voice due to the presence of helium. Repeating the phrase "kill the humans", SV7 turned on the newcomers, beating Uvanov to the ground. It began to choke Toos, but the Doctor thrust a laserson probe through its head, deactivating it and saving her. With a rescue ship on its way to collect Toos and Uvanov, the Doctor and Leela left. (TV: The Robots of Death)