Thematic try :  1. Ra1 ?  Threat : 2. Qa8(Ra8)+  Kc7  3. Nb5 # with block

1....Bxc5  2. Qa8+  Kc7  3. Nb5+  Kd7 ! (3....Kb6 ?  4. Qa6 #)  4. ?

   1. Nd7+ !!

a)  1....Rxd7

     2. Rc8+ !  Kxc8

     3. Qa8+    Kc7

     4. Nb5 !  #  Selfblock.and block. Model mate.

b)  1....Ka7

2. Ra1+  Ba5

3. Rxa5+  Qa6+

4. Nb5 !  #  selfpin and selfblock with cross-checks. Model mate.