Robots were infiltrating the Federation. Someone was kidnapping people and substituting indetectable, synthetic imitations. Somewhere, aliens were studying the Federation, using techniques beyond human developments. The trail led back to Cerberus and the Lord who ruled that planet.
Cerberus, however was one of the Warden Worlds-and those Worlds were the untouchables of space. There a strange microscopic life-form invaded all matter, and anyone so infected died on leaving those Worlds. Men could go there, but never return.
But the Federation had its own techniques. They took a criminal named Qwin Zhang and stripped her mind of all memory and personality. Then they poured into that empty receptacle the full mind of the Federation's best operative. They exiled her to the prison world of Cerberus. The mission: Find the Lord who ruled, kill him, and take over. Too bad there were things about Cerberus they couldn't know!
Volume Two Of The Four Lords Of The Diamond.