We know from our work on Anastasia’s mate that the f5 and d5 squares, among others, can be strong positions for a knight because from there it can jump to e7. Now you can see that e4 and g4 also can be strong positions because from there a knight can jump to f6—a classic post on which it can help execute the Arabian mate. Of course the f6 square has to be safe and other conditions must be met as well; which squares really are best for your knight naturally depends on how the rest of the board is configured. Anyhow, here you observe that f6 is open for the knight; that Nf6 will force the king to h8; that this will create the diagonal knight-and-king kernel of the Arabian mating pattern; and that then you have a rook on c7 ready to jump to h7 and mate—except that h7 is protected by the bishop on g6. The remedy is simple: a capture of the guard with 1. QxB+, requiring the reply h7xQ. Now the mate plays itself. 2. Nf6+, Kh8; 3. Rh7#.