A9s, top pair on suited flop

MP1 is a LAG based on like 40 hands, MP2 unknown.

Party Poker 2/4 (7 handed)

Preflop: Hero is UTG with 9[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/club.gif[/img].
Hero calls, MP1 calls, MP2 raises, 4 folds, Hero calls, MP1 calls.

Flop: (7.5 SB) 4[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/spade.gif[/img], 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, MP1 checks, MP2 bets, Hero raises...

I really don't like this kind of situation, and didn't know what to do really. Is perhaps just calling and then betting a non-spade turn a better line?