Chess FEN

I have this interesting Android game: iChess Tactics. This provides me hundreds of puzzles to solve. It can export its puzzle in Forsyth-Edwards Notation notation. (Hey how come I can't easily screenshot my phone)

I found a very nice FEN viewer in DHTML Goodies. Enter the FEN notation and it will draw a board for you! (No, you can't play right on it, it is just a viewer.)

Chess can be full of surprises... one wrong move can cost you the game. In this puzzle, the game is just barely started. Almost all pieces are here. Black to move, can you spot the killer move?

FEN:
rnbqkb1r/pppp1ppp/8/4P3/6n1/7P/PPPNPPP1/R1BQKBNR b KQkq - 0 1
Chess Piece Type: Motif Cases Merida Alpha Smart Leipzig