It was a dead giveaway. This was not his Wanda. She may have become her if she'd ended up on his version of the station instead of this one, or it may be another entirely, or the one he knew but different because she had experienced more or less in her own reality. But not his. He had already been surprised his luck had lasted this long, that would have been too much.
He could sense her wariness, almost feel the hum of her nerves and confusion in the air, so he didn't move any more, just standing where he had stopped until she felt better about him. "No one is entirely sure." he told her, "The theory I've always thought made the most sense is a pocket universe. It's a space station, but not in our...but it doesn't exist in the same place you're from. It's in its own space and time and steals us to occupy it." There was no point in easing her in or sugarcoating anything with Wanda. She was strong enough and smart enough to handle it. She could peer into his mind to find out anyway, and he wouldn't have resisted if she tried.