1.d4? (2.d5#),

 1...fxe5 2.Bg4+ Kf6 3.dxe5#,1...cxd4!

(1.Bh5? f5!  1.Qf2? Rg8!)

1.Bg2! -2.f5+ Kxe5 3.Qb2# (A),2...gxf5 3.exf5# (B),

1...fxe5 2.Qb2 (A)  Kf6 3.Qxe5#,2...exf4 3.Bh3#,

1...f5 2.exf5+ (B) Kxf5 3.Bh3#,2...gxf5 3.Bd5#.

Threat mates turn into immediate parries in solution.