The scenario is simple. A does not mention B when asked, and then A balks at the idea of executing him.
Why?
Scenario 1--
A arrives at close to the same time as myself. He intentionally withholds B, but isn't aware of C's presence.
Problem: Why the devil would he shelter B? They worked together briefly. B has a more gung-ho approach, he engages more personally in the preparation and combat aspects, and his attacks are flashier in nature. I would have expected a level of annoyance, not alliance. Particularly not against the man who hired them both. I've known him for years. B must have been familiar only through reputation.
But if I've read the situation correctly, not only did he try to keep him from my notice, but he reacted with disagreement when told to kill him.
Why?
Scenario 2--
He arrived here before I did. He intentionally withheld C, but assumed B was with me.
Motivation: He didn't want to be involved in an assassination in such a small community.
Problem: Why would he not ask that his contract be suspended until he had the promise of payment? It was an out. He failed to take it. He could have ended our association until I presented him with an offer that snagged his interest, or until we returned home.
Problem: Mr. Death, be bothered by killing anyone, at any time?
Problem: That narrowing of his eyes--what was that a signal of? Disagreement, defiance, suspicion? In context. . . defiance.
Scenario 3--
He's loyal.
Problem: I don't believe that for a moment.
Conclusion: Something happened. I can't imagine what. B rescued A from vampires? A brought something with him of value to B, and hired him to help him fit in seamlessly? This is a hostile lot--but A can seem so quiet and inoffensive, until he's sighted the target, that he should be able to fit in with relative ease.
Still, the seed is planted. He is aware now that B's tendency towards disclosure to his new friends could rebound disastrously on him at any given moment.
C is my own problem. But what can he do? There's no proof here, and he will need proof to turn the community against me.
So long as I remain calm, I can stay here indefinitely.