White's position looks solid and well-fortified. Is there a weakness? Yes: the kernel of rook-plus-queen on a diagonal, as White has here on e2 and f1, once again is a vulnerability. The pieces are on a light-squared diagonal, so Black just needs to get his light-squared bishop into line with them—with protection, of course. He plays Ba6, made safe by the knight on b8, and wins the exchange after White’s queen moves.

Before plunging ahead, though, take a moment to ask whether White would have any defenses against Black's skewer. One idea to consider is an interposition: can White block the attack by planting something in its way? Here he could, with Nb5. But notice that White's knight then has pinned itself to its queen. So Black rethinks the resulting position, now looking at it as a pin, and goes after the paralyzed knight with c7-c6. White could add a defender with a2-a4, but it doesn’t matter; extra defenders are no consolation when one of your pieces is about to get taken by a pawn.