Correct answer: Qb51...O-O-O 2.Qa6# 1.N:b6?? (2.Rf8#) but 1...Nf6! 1.Re7+?? 1...Kd8 2.Qf8# but 1...N:e7! 1.Qb5! (2.Rf8#) 1...K:f7 2.Qh5#
