Chess Tactic

Black to move. What should black do?

Carlsen missed a chance to win the first game of the match as black. Can you find the right plan here? There are a couple of winning moves that are related here, but one should stand out.

No. 1-1

When I first saw this game, I thought ...Rg3 was the obvious idea here, sacrificing the Exchange for a pair of connected passed pawns deep in the heart of White's position. After N:g3 hg, Rg2 Black's Q gets to the queen side and wreaks havoc.