straight on a monotone flop

[styleish]

What's my move here? Villain is 27/10/4.6, hasn't been very out of line. Button is pretty crazy, overbetting a bunch of pots. villain seems to be waiting pretty patiently for a chance to double up through him.

sorry no hh, going from memory, stack sizes may not be exact
PP NL25 (6 Max)

SB(Hero): 70
BB: 35
UTG: 35
MP: 25
CO (Villain): 25
Button: 125

Preflop: Hero has 53o (no hearts)
UTG calls, MP folds, everyone else calls, BB checks

Flop comes: 4 [img]/images/graemlins/heart.gif[/img]6 [img]/images/graemlins/heart.gif[/img]2 [img]/images/graemlins/heart.gif[/img]
I bet pot (1.25), folds to CO who makes it 4, button folds, hero...?

i feel villain can either have something like AhQx-Ah9x, a small flush, a set, or a bigger pair with a heart (not so sure about this because don't really see a reason he would raise with it but he is pretty aggressive and doesn't like to call). how is my thinking here? and what's my move?