Set gets donked on river on straight card

[DavidC]

Villain's unknown.

Board is ktx rainbow. Hero has raised pf vs some limpers at a short table (5-6 players) and gotten a lot of calls. Hero has TT.

Unknown villain calls to river (check-calls) oop, then donkbets on a rivered 9.

KTxx9

It completes QJ, but also T9.

-------

No flush draw has been completed, and I can't remember if there was one on the turn or not.

Villain is completely unknown after four hands.

----------

My line here, which may be retarded, is to raise and fold to a three-bet.

Help!