400NL - flopped set facing scary action on the turn.

[Mossberg]

villain is 23/13/3 (800hands) tagfish reg. Standard to just let it go here? He is kinda weak so I didn't think he would lead this flop with just a random flush draw -- BB is like a 75/50 megafish. Also, if he had something like Ah6h or 86s or Ah3h I expect that he just gets it in on the flop.

Blinds: $2/$4
5 players
Converter

Stack sizes:
UTG: $491.00
CO: $641.20
Button: $390.00
SB: $452.00
BB: $953.55

Hero is dealt 5[img]/images/graemlins/diamond.gif[/img]5[img]/images/graemlins/club.gif[/img]

Pre-flop: (5 players)
<font color="#cc0000">UTG raises to $14</font>, Hero calls, Button folds, SB calls, BB calls.

Flop: 5[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/diamond.gif[/img] 4[img]/images/graemlins/heart.gif[/img] ($56, 4 players)
<font color="#cc0000">SB bets $40</font>, 2 folds, <font color="#cc0000">Hero raises to $128</font>, SB calls.

Turn: K[img]/images/graemlins/heart.gif[/img] ($312, 2 players)
<font color="#cc0000">SB is all-in $310</font>, Hero _________?