Figure[Black to move]

Again White’s king can take Black’s knight on e2. Black has a bigger problem, too, for White threatens to mate by playing Qf7+, forcing Black’s king to h8 and then mating on f8 (his queen goes there and gets taken by Black’s rook; then White has RxR#). Yet Black can address both problems with the ingenious Qe8. See what this does: now Black’s queen is on the e-file, ready to defend the knight once his bishop on e5 has moved out of the way. In other words, the kernel of a discovery has been created expressly to protect a fellow piece at the other end of it. Indeed, this does better than protect the knight and defend f7 against mate. It means that if White plays KxN, Black then has a discovered check with Bb8+, attacking White’s queen as well as his king.

We aren’t finished; don't forget to consider what White would do about the check you are imagining when Black moves his bishop out of the way. White could interpose his rook with Re3, not only blocking the check but attacking Black’s queen. So then what? Black looks for another check that would then be possible; so long as he keeps White busy with checks, the capture BxQ will still be waiting for him afterwards. Here Black’s next check is Qb5+. White again can interpose the rook, but this time it only blocks the check; it can pose no threat against a queen attacking along a diagonal. Now it's safe for Black’s bishop to take White’s queen.