The contents behind door number three can vary depending on the scenario or context. It could represent:

* **A prize or valuable item:** In game shows or contests, door number three may contain a grand prize or a desirable item that the contestant aims to win.
* **A surprise:** It could reveal an unexpected guest, a special gift, or a surprising experience.
* **A danger or challenge:** In some stories or adventure scenarios, door number three may lead to a perilous situation or a difficult task that the protagonist must overcome.
* **A hidden object or secret:** It could conceal an important object, a clue, or a secret passage that progresses the plot or reveals vital information.
* **A choice or decision:** In metaphorical or decision-making situations, door number three may represent a particular path or option that comes with its own set of consequences.
* **A continuation of the story:** In a book, series, or video game, opening door number three may lead to the next chapter, level, or storyline.

The specific contents behind door number three depend on the context and the intentions of the creator or storyteller.