The defender that cannot move

Material is level and Black's rooks are doubled on White's third rank, which usually means the game is already over. Look closer. One of them is pinned to the king by the white queen and cannot legally move, so the second rook is guarded by a piece that can never recapture. White's next move goes straight at that. Find the move that repairs the defence before it gets tested. · Positional Chess Puzzles