TPTK on flop, but then....

[Bats]

I couldn't figure out what this guy was doing. What do I do here?

Paradise Poker 0.50/1 Hold'em (10 handed) converter

Preflop: Hero is MP2 with A[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/spade.gif[/img]. UTG posts a blind of $0.50.
UTG+1 calls, <font color="#666666">1 fold</font>, MP1 calls, Hero calls, MP3 calls, CO calls, <font color="#666666">2 folds</font>, UTG (poster) checks.

Flop: (6.50 SB) J[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/spade.gif[/img], T[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(6 players)</font>
UTG checks, UTG+1 checks, MP1 checks, <font color="#CC3333">Hero bets</font>, MP3 calls, <font color="#CC3333">CO raises</font>, UTG folds, UTG+1 folds, MP1 folds, Hero calls, MP3 calls.

Turn: (6.25 BB) K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, MP3 calls, CO calls.

River: (9.25 BB) 9[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>

Final Pot: 9.25 BB
<font color="#CC3333">Hero bets</font>, MP3 raises, CO folds.

<font color="#CC3333">Hero ?????</font>,

I had TPTK on the flop, but flopped straights are possible and draws almost certain. But with top pair I bet, get raised and call. Could be beat right here with a straight, but who knows. Turn gives a straight to anyone with a Q, and a paired K beats me, but I bet figuring I'll fold to a raise. No one raises me, so no one likely has a straight or a K. River gives me two pair, I bet. MP3 who has been calling and checking raises and the CO who raised the flop folds. What's likely going on? Do I fold, call, raise?