Kellman visited Neo Phobos and was paid in gold by a Vogan faction led by Vorus to ally himself with a group of Cybermen and lure them to Voga — as he learnt the asteroid was called — so they could be destroyed by a rocket. Kellman obeyed the Cybermen's instructions to use the Cybermats to infect the Beacon's crew with a plague, which killed off everybody except Commander Stevenson and Lester. The Fourth Doctor later exposed him as the perpetrator and he was taken prisoner. When the Cybermen boarded the ship, he was allowed to transmat to Voga where he tried to find Vorus.