3-bet by a poster... now what?

[ArturiusX]

Party Poker 5/10 Hold'em (6 max, 5 handed) converter

Preflop: Hero is UTG with T[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/spade.gif[/img]. MP posts a blind of $5.
<font color="#CC3333">Hero raises</font>, <font color="#CC3333">MP (poster) 3-bets</font>, <font color="#666666">3 folds</font>, Hero calls.

Flop: (7.40 SB) T[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/club.gif[/img], 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP bets</font>, Hero calls.

Turn: (4.70 BB) 6[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP bets</font>, Hero calls.

River: (6.70 BB) 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP bets</font>, Hero calls.

Final Pot: 8.70 BB

No reads, as he's new to the table. I hit middle pair, I decided to call down, thinking he might have a mid pocket pair, or maybe KQ or misc random. Who folds?

[ghostface]

I fold the turn.