Two Bagels, one moustache. Doc & Co are split across time in the first part of the Black Guardian Trilogy
On a luxury cruiser, eight mutated space chaps dressed like Björk are deeply regretting their crimes. Centuries prior, they stole a metamorphic symbiosis regenerator from Gallifrey with the intention of turning themselves into Time Lords. Alas, it only served to give their brains a comb-over and subject them to eternal suffering. All they need now is any random Time Lord or Lady to sacrifice their regeneration energy in order to end it.
Meanwhile, coincidentally, The Black Guardian has appeared on Earth and recruited highschooler Turlough, a cocksure cockhat with coincidental knowledge of space and time attending a school where, coincidentally, works Alistair Gordon Lethbridge Stewart. Remember Brigadier Bagels? Well, coincidentally, he barely does. And as a matter of further coincidence, The Doctor and his companions are about to be drawn into a deadly game that might turn Doc into a regular schmo.