Mate in 4.
Actually, there is one other mate in 4 with the rook on b8. 1 Qf5 Kg8 2 Qxh7+ Kf8 3 Re1 with mate next (1 Rd1 almost counts as one more, except for 1... Re8).
Actually, there is one other mate in 4 with the rook on b8. 1 Qf5 Kg8 2 Qxh7+ Kf8 3 Re1 with mate next (1 Rd1 almost counts as one more, except for 1... Re8).