A Seventh Doctor novel with Ace.
After the end of the interstellar Tulkan wars, the militaristic Tulkan War council was sentenced to memory-wiping and incarceration in a penal colony. Their weapons, advanced slavery devices and planet destroying armaments in development, hidden in a secret cache before the end of the war, are bound to remain secret forever, the access codes to their stasis chamber wiped with the Tulk's memories. But in an old people's home in Scotland, Dr Elizabeth Brunner, Unit scientist and daughter of one of the Alzheimers patients, has noticed disturbing happenings, and calls on her old friend, the Doctor, to investigate.
What he and Ace find goes beyond disturbing, with campers murdered, the denizens of the home wired up to some sort of enormous calculating machine, and Ace being followed around by a mysterious figure, always remaining just beyond the edges of vision. They receive help from Annarenes, members of a race devoted to keeping the Tulkan menace down, but help from any quarter has to be regarded with utmost suspicion. Nothing, here, is sure to be what it soems...