It's possible. There are occasional slips in the Underground's consistencies, an overlapping of similar realities. It rarely clashes so greatly as this, however, thought it happens once in a great age.
I do not wish to offend you if that is your understanding, but I am married to Sarah. I do not know of this Mikhail you speak of, nor do I know even your name. It's irrational to think that I could would respond kindly to a stranger in my home, even if it is with the most innocent of intentions. And if I knew where Andivad had slipped off to, I would ask why it is that he allowed you to stay, knowing bloody well that it would upset me.
Stay in what you believe is your chambers for now, and we shall discuss this burden once I find the bloody little blight that left this mess for me to deal with.