Fold. Unless you are up against a player who can read your mind or who knows exactly how you think, folding is best in a typical $10-$20 game against decent opponents. There is $130 in the pot and it costs you $20 to call. These are pot odds of around 6-to-1. What are your outs, assuming your opponent has a better hand? A seven for sure, but that is only two outs, a 23-to-1 shot. Is an ace an out? Only if he doesn't have trip fours or a straight. In the most optimistic case (other than a bluff), you have five outs with any ace or seven, which is an 8-to-1 shot, so the pot odds are still not there even in this rosy scenario. Bottom line is that there will be a high percentage of cases where you are playing two outs, making your call totally wrong. There will be a small percentage of cases where your call is only slightly wrong, because you happen to have five outs instead of two. To play on here is to basically put your opponent on a bluff or semi-bluff. Furthermore, at the time the middle limper raised, there are two players in the hand, you and the small blind. If he is bluffing or semi-bluffing, he is doing it in a multi-handed pot, which makes those types of plays more unlikely. The other problem with playing on, based on the shaky assumption that he is bluffing, is that you will end up calling a river bet as well, so it will cost $40 to see the hand through (not just $20).