Now there are three doors with statements on them:
There is nothing behind the third door.
There is a trap behind the first door.
There is nothing behind this door.
Your guide says: There is treasure behind one of the doors, trap behind another one and there is nothing behind the third door. The sign on the door leading to treasure is true, the sign on the door leading to a trap is false, and the third sign might be true or false.
Which door will you open, if you really really want the treasure?