Good Morning Puzzlers, AS usual, Paul has done an excellent analysis of this problem and everyone interested is encouraged to read through it carefully. My short answer follows. The best move is: 1. Ng5+ Principle:Although both queens are currently en prise, there are some interesting points to notice. The black bishop at f6 is pinned and thus immobil. And the black knight at e6 is only defended by the king. White avoids simply trading queens by the priority of check: 1. Ng5+, now if black moves the king away from the knight the white queen takes the knight and if the black king moves to either f8 or g7, the knight and queen are lost in a royal fork! So black is forced into: 1. ... Nxg5, and then white plays: 2. Rd7+, winning the queen for a rook.