The 30 second chess tactic

Black to play and win

Canberra player Victor Braguine is currently enjoying a bit of a chess holiday in Europe, and has sent me the diagrammed position. He was Black against a higher rated player, and had good chances with an extra piece against two pawns. Almost at the time control he thought for a bit and then swapped queens with Qd4. After that he could not turn his extra piece into a win, and the game was a draw.
But he asks, can you find the winning move (which he missed) in under 60 seconds?
(SP: At my first attempt I spotted the correct move, but then I discarded it, after not finding the correct follow up)