Tactical Puzzle 4

In this position, you are Black. You are down in material, down a knight for two pawns. The two extra pawns are doubled on the g-file and soon one or both of them can be lost. You are set for a defeat but you got one last chance to avoid it as he has got a weakness which you can exploit. Since it is your turn, you can mate him in three moves!

The answer is down (for ones who can't find the solution)

Here is the answer:

The only real try you can make to threaten mate is 1... Qe5 but that is stopped by the simple 2. g3. No other move makes a threat ans so this is the best and ONLY move to avoid defeat:

How is this? A superb problem! And keep your eyes out for more ones like this.