Put on your Indiana Jones hat but don't get out the whip - you're gonna need your brain to solve this riddle.
TED-Ed, the webinar gurus and educators, have come up with some brain-scratching riddles in the past, and this new one is a bit challenging.
Yourself and eight graduate students are exploring a temple when you knock into an artefact, which causes the collapse of the ruins.
You're fleeing the falling rubble but come to a junction, with four possible exits, each of which will take 20 minutes to explore and then 20 minutes to return to alert the others as to whether it is the way out.
You think you have an hour to find the way out.
The artefact has also possessed two students, who will now lie to attempt to trap you all in the temple forever.
You do not know which students, but you do know for certain that you are not possessed.
So how do you pick the way out, with your team of eight students, without being tricked?
Watch the full video, below to find the answer, and let us know how you did in the comments: