100NL TPGK vs maniac, multiway flop

MP1 is a total donkey maniac, with an added read that he bets draws weakly. He could have anything from K3 to QQ, but is likely not on a draw. Others are unknown. Hero has been seen playing a nut flush draw very aggressively a few hands ago.

Party Poker No-Limit Hold'em, $1 BB (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver Cards)

BB ($166.30)
UTG ($107.55)
UTG+1 ($102.94)
UTG+2 ($91.55)
MP1 ($189.10)
Hero ($100)
MP3 ($98)
CO ($175.45)
Button ($88.50)
SB ($29.01)

Preflop: Hero is MP2 with http://www.flopturnriver.com/phpBB2/.../smiles/kc.gif, http://www.flopturnriver.com/phpBB2/.../smiles/qc.gif. UTG posts a blind of $1. SB posts a blind of $0.50.
1 fold, UTG+2 calls $1, MP1 raises to $4.5, Hero calls $4.50, 2 folds, Button calls $4.50, 2 folds, UTG+2 calls $3.50.

Flop: ($19.50) http://www.flopturnriver.com/phpBB2/.../smiles/3d.gif, http://www.flopturnriver.com/phpBB2/.../smiles/qh.gif, http://www.flopturnriver.com/phpBB2/.../smiles/jd.gif (5 players)
UTG+2 checks, MP1 bets $18.55, Hero???