Puzzle no. 1 Solution

Black to play

1…. Rxg2+ 2. Kh1  Rxf2+ 3. Nxc6 Rh2+  4. Kg1  Qg2 mate

Instead of 3. Nxc6 White can block the check but 3. Bd5 changes nothing and 3. Nf3 allows Rxf1