White has lots of ways to give check with his queen, so inquire into the consequences of each. The most interesting is Qe6. Why? Because it moves the queen behind White’s knight and Black’s queen on the e-file; it thus puts three pieces on a line in the familiar formation for a discovered attack. Again, moves that so create the kernel of a discovery usually need to force other changes on the board that keep the enemy busy and that may also create the remaining elements of the tactic. Here Qe6+ not only creates the kernel of a discovery but also gives check, forcing the king onto either h5 or h7. Either way, with Nf6+ White’s knight will give check and unmask QxQ.