The wanderer arrives at a fork in the road taken care of by two guards. One of the two possible branches leads to life while the other one means death. One of the guards always tells the truth but the other guard always lies. Apart from this, the two guards are identical, they even look the same, so that it is not known which one is the liar. The guards know each other and they know which branch means life and which one means death.
How can the wanderer determine, with only one yes/no question, which road leads to life?