The young man made the serious mistake of falling in love with the king's daughter and engaging in a passionate love affair with her.
Among his courtiers was a young man of that fineness of blood and lowness of station common to the conventional heroes of romance who love royal maidens....This love affair moved on happily for many months, until one day the king happened to discover its existence. He did not hesitate nor waver in regard to his duty in the premises. The youth was immediately cast into prison, and a day was appointed for his trial in the king's arena.
What the king apparently objected to was not the love affair itself but the fact that the young man had too low a "social station" to dare to engage in such a relationship with his daughter. There may not have been any law against doing what the young man was doing, but the barbaric king could make his own laws. And that was what he was doing. At least the king was giving the poor fellow a fifty-fifty chance to stay alive and even to marry a beautiful girl if he chose the right door.
The fact that there is a beautiful girl behind one of the two doors is what causes the problem. The princess knows which door conceals the tiger, and she would undoubtedly direct her lover to the other door if it did not conceal a beautiful girl whom her lover would immediately marry. Whatever was going to happen happened a long, long time ago. The story opens with the words:
In the very olden time there lived a semi-barbaric king...