Nobody knows for sure, and we will never know! Isn't that maddening? The surprise, unresolved ending of the story has engendered many conversations about what the young man found behind the door. Did the princess love him enough to save his life by giving him up to another woman, or was she jealous and completely selfish? Would she rather see him dead than married to a beautiful woman whom she despised? The young man's fate depends on how the reader views the princess, in particular, and human nature, in general.
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Although the author doesn't explicitly answer this question, there is more evidence to support the tiger emerging. The princess is portayed as somewhat barbaric, jealous, and possesive.