@Santosh Kanatia If I may spoil, There are two ideas, Nc2+ Kb1 Na3+ Ka1 Bh6, only option for Black is to move the knight, Bg7+ knight comes back on c2, and then Kf6 getting closer to the knight by this manoeuvre, obstructing the bishop's diagonal, avoiding stalemate, until you can simply make Bxb2#