Villian is complete unknown
I check-called Flop for pot control and to see what hits on Turn
Then he Pots it on Turn on a non-flush, but straight card

Winning Poker Network (Yatahay) - $0.02 NL - Holdem - 7 players
Hand converted by PokerTracker 4

MP: 78 BB (VPIP: 21.57, PFR: 5.88, 3Bet Preflop: 0.00, Hands: 51)
CO: 53 BB (VPIP: 14.71, PFR: 11.80, 3Bet Preflop: 3.74, Hands: 747)
BTN: 18.5 BB (VPIP: 50.00, PFR: 18.75, 3Bet Preflop: 16.67, Hands: 16)
Hero (SB): 51 BB
BB: 50 BB
UTG: 35 BB (VPIP: 30.00, PFR: 10.00, 3Bet Preflop: 0.00, Hands: 11)
UTG+1: 89 BB (VPIP: 19.44, PFR: 2.78, 3Bet Preflop: 0.00, Hands: 36)

Hero posts SB 0.5 BB, BB posts BB 1 BB

Pre Flop: (pot: 1.5 BB) Hero has 4 8

fold, UTG+1 calls 1 BB, fold, fold, fold, Hero calls 0.5 BB, BB raises to 3 BB, UTG+1 calls 2 BB, Hero calls 2 BB

Flop: (9 BB, 3 players) 8 T 4
Hero checks, BB bets 6.5 BB, fold, Hero calls 6.5 BB

Turn: (22 BB, 2 players) 5
Hero checks, BB bets 21 BB, [color=red]Hero????

Fold pre. As played OTF I'd C/R. As played OTT I'd shove.