I didn't ask how he'd got into my apartment. Instead, I asked
Have we met at any time in the past?
I asked the question, already knowing the answer.
He answered simply "No."
So how can we meet now? We both know it's impossible.
Again, simply, "Yes."
A time traveller cannot go back in time and meet himself.
He agreed. "But forward in time?"
I frowned. But no, a physical impossibility. You cannot exist as two entities simultaneously.
And we frowned in unison at our situation.
Then he shrugged, said "If I discover anything, I'll return" and disappeared.