Puzzle from the Daily Chess Puzzles

Here is the puzzle from the Daily Chess Puzzles yesterday '29/8/09' from that is was white to move and win in 4 moves, well here the same position but this time is black to move and win in 4 moves.

 What the answer ?

I think it can be done in 3 moves with Qb2+ Bb6  Qxb6+ Ka8 or Ka7 Qb7#

Incorrect because of 1...Qb2+  2.Bb6+ discover check by the rook on  c8 ! then white will win in 6 move later.

How about Nxc8+ (discovered check by the black Queen) Kxc8 (if instead of capturing White tries Ka8 then Ra7++) Rc7+! when either of the following lose:

(a) Bxc7 Qxc7+ Ka8 Nb6++

(b) Kb8 Qb2+ Ka8 Qb7++

That is correct deadlyduck with the line (b) for (a) Bxc7 Qxc7 is mate. Well done.

Nice! I'm not really good at solving puzzles visually. : )

ADK