Mate in 3

Observe that Black is already in zugzwang. If the bishop on b5 moves, 2.Qa5# follows at once. The rook moves 1...Rc3 and 1...Rc1 are met with 2.Bxc3 and 2.Bxc1, respectively, leading to 2...B~ 3.Qa5#. Other moves of the rook result in immediate mates: 1...Rxb4+ 2.Qxb4#, 1...Rxc5 2.Nxc5#, 1...Rc2+ 2.Qxc2#, etc.

Thus, it is clear that we are looking for a waiting key. 1.Qf5! is an intuitive choice, as it keeps the queen trained on the crucial squares c2 and a5, preserving most of the set play above.

Now, after 1...Rxb4+, 1...Rc1, or 1...Rc3, White has 2.BxR!, making 3.Qa5# inevitable. The star variation, however, is 1...Rxc6, met by 2.Qc5!—a clever switchback of the queen to extend the zugzwang—so that Black’s every response enables mate on the third move: 2...B~ 3.Qa5#, 2...Rxc5 3.Nxc5#, and 2...R~ 3.Qc2#.

A dainty and elegant riddle!