You are in front of the same two doors (one door leads to incredible wealth and the other leads to nothing of value but you do not know which is which). There are three other people (who do know which is which) standing in front of the doors. One always tells the truth and one always lies. The third person is unpredictable - telling the truth or lying randomly. Of course, you have no idea which person is which.
You can ask two Yes/No questions (one at a time to only one person each) in order to find the riches. What questions do you ask, and to whom, to find the riches?