P.S. Another thought for you to consider: if Ann (or others) were to discover that Peter is from the future (and assuming that they believed this to be the truth), naturally they'd expect that he could give them information to help them win the war -- or maybe he knows how to build some sort of futuristic weapon, right? But, of course, from Peter's POV, he really has no useful info to offer; he's not a research physicist, and he doesn't know the specific details of Hitler's invasion of the USSR, so he could only tell them, unhelpfully, that "I know that you'll eventually drive out the Germans, and then Hitler will suck on a bullet, about four years from now..."

I remember once reading a sci-fi story in which 22nd-century scientists build a working time machine, and they somehow manage to "capture" a 32nd-century man and bring him back to their time. The guy from the future is only mildly surprised at suddenly finding himself a thousand years in the past (evidently time-machines exist in his era, but only the super-rich can afford to use them), and is mostly delighted by how primitive everything is, as though he's a tourist at a Renaissance Faire. "Oh my gosh, so this is what life was like a thousand years ago... no transporter beams, no antigravity clothing, no telekinesis helmets, no faster-than-light spaceships! It's all so quaint!"

Of course, the 22nd-century scientists are eager to hear more about all these technological marvels, and how to build them -- but how the hell should he know? He's not an engineer or scientist, he's just a middle manager in the accounting department of an insurance company in one of the less-fashionable cities on Mars...