Solution
1. Bxd6 Qxd6 2. Rxc5! wins the knight since the rook is indirectly defended by a discovered attack, ie. 2… Qxc5? 3. Bxf7+ followed by Qxc5
1. Bxd6 captures the defender of the c5-knight and combines the sequence with the idea of an discovered attack, Bxf7+.