"Yes," he says, and there's an element of both 'yes' and 'why do you care' in his own tone. But please, ask him probing personal questions. If he's in a good mood, his answers might even be true.

Tonks would be correct in presuming that he's got a bit of a shadiness to his character, but in this case, it's entirely unwarranted. There isn't anything suspicious about what he's doing (this time); he's just a private person.

Gene looks at the offered hand, considers ignoring it, and then remembers Tony's injunction to make friends. So he shakes it. "Gene."