[lazlo]

I would fold. Your chances of hitting are approximately 1 in 3, his $15 bet makes your potential winnings a mere $30.50. Realistically you need a 50% of hitting on the river to justify a call. Remember that even if a high card is all he has - he still has more outs than you on the river. You could always try bluffing it, but I wouldnt try it in this inatance.