White is unhappy to see that Black has hit him with a knight fork from e3. But since the fork doesn't include a check, White’s response isn't tightly forced. He can think about taking the offensive rather than attempting damage control. So ask one by one: are any of Black’s pieces loose? Yes: the knight at e3 that is inflicting the fork. This is the target. White’s queen can attack it, but not while giving check; the Black king is hidden behind the bishop at g7. So look for other checks that might force the king into a vulnerable position, and find 1. BxB+, KxB. Now Qd4+ forks and wins the knight. Since White's move gives check, Black never has time to carry out the knight fork he had been threatening.

This problem illustrates the importance of not panicking when threatened with a knight fork. It also is a reminder of why knight forks against two non-kings often are so much less effective than knight forks that give check. Here White doesn’t have to move his king, and so has time to mount a fresh threat of his own.