What is the Best Plan?

I was playing with my student, we shall call him J, today and we played a very interesting game. I thought it would be very instructive for everyone here at chess.com. The diagram below is the critical part in the game. It is black's move. What do you think is the best plan? 

I won't give the answer now. Look for that in my next blog post. In the meantime, why don't you tell me what you think the plan is.