Chess Puzzle

Black to move and win:

highlight to see anwser below
[
Meister,P (2445) - Brynell (2405)
London 19901...Rexc7! [ 1...Rexc7 2.bxc7 Nb4+ 3.axb4 Ra8+ 4.Kb1 Ra1#] 0-1

]