OK, not really, but that's the joke that the
"You're the super sleuth," said Murray-arty. "Figure it out."
Cumberbatch resisted at first, insisting, "I'm really just an actor." Eventually, though, with some help from the Count (not Watson), he was able to enter his own mind palace and get to the bottom of the mystery.
We won't spoil the fun by revealing the answer.