Thursday puzzle / game

Thursday puzzle / game

Black to move

In the position above Black can secure an advantage by playing Nxd3.  However, he has something much stronger.  Can you see it?

The position is taken from Stephen Peters vs Mike Waddington, which Mike kindly sent in with his own annotations.  The whole game is very nice and his spot in this position is excellent.  You can see the whole game and hence the solution (move 26) below.