QQ in huge multiway pot, ace flops

UTG+2 is a tight and aggressive player and certainly knows what he is doing.

Cryptologic 0.50/1.00 Hold'em <font color="#0000FF">(10 handed)</font> link

Preflop: Hero is UTG with Q[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">Hero raises</font>, <font color="#666666">1 folds</font>, <font color="#CC3333">UTG+2 3-bets</font>, MP1 calls, <font color="#666666">1 folds</font>, MP3 calls, CO calls, <font color="#666666">3 folds</font>, <font color="#CC3333">Hero caps</font>, UTG+2 calls, MP1 calls, MP3 calls, CO calls.

Flop: (21.50 SB) 7[img]/images/graemlins/spade.gif[/img], 3[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(5 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">UTG+2 raises</font>, MP1 calls, MP3 calls, CO folds, Hero calls.

Turn: (14.75 BB) 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(4 players)</font>
Hero...

What do I do? There are 5 players in this huge pot! Somebody must have an ace.....?