Mate in 3

Black has adequate defences for immediate attempts to mate with the f4 knight. 1.Sh5? Bc7!; 1.Sh3? Bd8!; 1.Sd5? Bd4!
1.Bf7 threatens mate at g6. Black can defend by moving the b6 bishop, and in four variations the f4 knight selects the continuation which will decoy the bishop into interfering with the rook. 1...Bc5 2.Sh5 threat 3.Sg3; 2...Bd6 3.Bg6; 1...Bd4 2.Sh3 threat 3.Sg5; 2...Bf6 3.Bg6; 1...Bc7 2.Sd3 threat 3.Sc5; 2...Bd6 3.Bg6; 2...Rc6 3.Bd5; 1...Bd8 2.Sd5 threat 3.Sc3; 2...Bf6 3.Bg6. 1...Ba7 simply prevents the bishop from attacking g5, hence 2.Sh3 threat 3.Sg5. The threat is extended in the by-play variation 1...Rf8 2.Bg6+ Rf5 3.Bxf5.