Control the power

As Gurkirat had proceeded to the building and, ultimately, to the meeting with these fellows of his own free will, he didn't bear the men with the same suspicion as his companions. They merely received the same suspicion as any well armed human capable of killing him where he stood without breaking a sweat. In other words, he was probably just as paranoid. Part of what the man in leathers said had caught his attention, though. Some men had mastered their affliction and could change at will. But they were twisted.

"HA," he barked. When eyes turned his way, he realized he had said it out loud. Twisted, he thought wryly. I'm already pretty damn twisted. What's a little more?

"What's this you say about becoming a wererat? I need to know everything," Gurkirat stated. He was answered only by silence. "What!?" he said defensively. "I know a rat isn't the most exciting thing around, but after getting whipped by a wounded one, I think it's good enough for a lowly gnome."

(I want to know if what he says is true. Should I use sense motive? Or Perception? Or a knowledge check?)

Ok then. Knowledge (nature)
2+3=5

Sense Motive:
5