AKs calls big raise and keeps getting called down??

10 minutes at table, no reads, and this hand comes up:

Party Poker No-Limit Hold'em, $ BB :#A500AF(villain)/ (6 max, 5 handed) FTR converter on zerodivide.cx

saw flop|<font color="#C00000">saw showdown</font>

<font color="#C00000">BB :#A500AF(villain)/ ($25)</font>
UTG ($15.75)
MP ($18.05)
Button ($49.20)
<font color="#C00000">Hero ($24.40)</font>

Preflop: Hero is SB with A[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/club.gif[/img]. Hero posts a blind of $0.10.
UTG calls $0.25, MP calls $0.25, Button calls $0.25, <font color="#CC3333">Hero (poster) raises to $1.4</font>, <font color="#CC3333">BB :#A500AF(villain)/ raises to $4.25</font>, UTG folds, MP folds, Button folds, Hero calls $3.

Flop: ($9.75) A[img]/images/graemlins/heart.gif[/img], 6[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $2</font>, villain calls $2.

Turn: ($13.75) 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $3</font>, villain calls $3.

River: ($19.75) T[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $5</font>, <font color="#CC3333">villain raises to $15</font>, Hero calls $9.90 (All-In).

Final Pot: $49.65

Your comments on flop, turn and river please. if you would call the river, please state why. thanks from a struggler in the trenches