This tactic comes from a game a friend of mine played a little while ago. When we sat down to review the game, we realized there was a tactic around this position, take a moment to see if you can find it:
The key to this tactic is to realize that the Queen has a limited number of safe squares. This allows us to enumerate and eliminate them one at a time until we discover whether or not the Queen is trapped (as it appears may be the case here). There are exactly 3 safe and effective ways to provoke the Queen.
If Be6 then either Qh5 or Qc6. If Qc5 then there is a very nice tactic to trap the Queen that proceeds
g6 Qh6 Bg5 Qxf8 Kxf8
And Black is up material. If Qc6 then there is only one move to attack the Queen, Bd7. After Bd7 the Qeen is free to move back to c5 and there is no threat as the Bishop has to continue moving to attack the Queen and the Queen can keep going between those two escape squares forever.
Thus we can eliminate Be6.
If Bb7 the Queen has h5 and c6. We already know that if the Queen ends up on c6, the tactic ends and we can’t trap the Queen. Therefore we can eliminate Bb7.
If c6 the Queen has either h5 or Qxc6. We know how h5 ends so lets try Qxc6. In this position Black has:
We can immediately eliminate moving the Rook because it guards the a pawn. If Bd7 then White may simply take the pawn on d6 and pin Black’s Bishop to the Queen. If the bishop moves, the Queens will trade and the tactic ends.
Therefore we move on to Bb7. If Bb7 White’s Queen is out of squares. Therefore White must play Qxb7 in order to gain some compensation and Black is free to pick up the Queen.
In either case (Qh5 or Qxb7) Black is wining the Queen thus from the original position we play c6 and the tactic unfolds from there.
I like this tactic because it’s an unusual Queen trap. You would not normally think that the Queen sitting in the center of the board is trapped, and the only reason this tactic works is because the Knight deep in enemy territory holds the b3 square. Tactics like these remind us that having complete vision of the board is important. Even pieces that don’t appear to be “in the action” make some contribution.