Figure[Black to move]

White recently played Ne2, a suspect move since it boxes in his f1 bishop; and now he has added the familiar pin of the enemy knight by playing Bg5. So Black plays the standard Nxe4, leaving his queen exposed to capture. If White takes the knight with his d3 pawn, Black has QxB and has won a pawn. If White instead plays BxQ, Black has Bxf2#: a startling mate made possible so early by the self-imposed inaccessibility of e2 to White’s king.