King Alistair III has been stricken with an almost incurable disease. His son, Crown Prince Rupert embarked upon a quest to find a rare herb which alone can save his father's life.

On the way, the prince was waylaid by evil wizard Morecash, who took him as a prisoner.

Wizard Morecash listened to Prince Rupert's predicament with rapt attention.

Next day, Wizard Morecash called Rupert and put forward a proposition saying to him, "I have precisely the herb that you are looking for! There are three rooms in front of you and each of them contain precisely one silver box. Only one of the rooms contain the silver box with the desired herb. Each of the other two rooms contain a silver box with poison. There are three signs in front of the door corresponding to each of the three rooms."

He further explained that, "The sign on the door of the room containing the box with the herb is true, and at least one of the other two signs is false."

           Here are the signs:

    I                    II                 III
Room II contains     This room            Room I
contains poison      contains poison     contains poison            

He proposed that if Rupert chose the correct room he will be set free, with his blessings, together with the box containing the herb. Otherwise, Morecash will hold him in eternal bondage.

Which room must be chosen by Prince Rupert in order to finish his quest?