And again, it's "Who has the move?". :P
White: Nxc4#
Black: Rxc2#
An original retro problem #29
Sort:
Without any analysis, 1...Rxc2+?! 2. Bd2, so only white can have a mate. Done.
OK, I'll try working through the intention properly. I'll look at this soon.
Alright, I have no doubt you know the solution already :)
I am terribly disappointed in myself now for even taking that long. Thanks shoopi.
I meant that you surely know the intended key move. Why would you be disappointed in yourself at all? You are very good at solving retros 
I'm surrounded by n00bs. :\
Black's mate in 1 would of course 1...cxd3ep#.
Correct. Analyse:
Black must have captured axb, which accounts for white's one and only missing man.
Black is missing 5 men, but they are not all valid captures. White's h pawn must have promoted, but it couldn't promote straight through black's h pawn. So either black's h pawn was captured or white captures hxg which is ultimately the same thing. This also means that black's e7 pawn is useless since it cannot promote, nor can it be captured by a white pawn at any point in the game.
White captures are gxf3 and bxcxd.
Black has no last move. -1 Nd3-b4? And white has no way to give check with Bc3 - no discoveries, and no extra black piece to allow Bxc3+. So white must have moved last. How to give black a move to retract?
-1 Q anywhere - c6? and -1... Nc6-b4 is still illegal.
-1 Na8/c8/d7? And neither -1... b6-b5 nor Kb6-a5 is possible.
-1 e4xd5? an illegal capture, missing 1 black capture.
-1 Be1-c3? -1... Nd3-b4 -2 c3xd4+? illegal because black's d pawn must have been captured straight, it couldn't have gone past white's d pawn.
-1 d3-d4? and black obviously has no legal move.
Therefore...
-1 d2-d4! (only move) -1... Nd3-b4 -2. Bd4/e5/f6/g7/h8 - c3+, and the position is released.
Mate in 1 with 1... cxd3ep#.
Not too difficult 
Mate in 1: