Find the kernel of the discovery. The pattern of knight-masking-bishop triggers thoughts of a discovered attack. If unmasked by the knight on g4, the bishop has an ideal target in Black’s queen. Also ideal is the knight’s target: it can give check with 1. Nf6+. It doesn't matter that Black can address the threat in various ways; he loses his queen in any event. Thus if 1. Nf6+, g7xN, then 2. BxQ; and if 1. Nf6+, QxN, then 2. NxQ+.