- The prince intends to monopolize all political power for himself, and doesn't want to share it with his future partner. He sees Psyche as the best option for queen as he considers her naive and ignorant, someone he can easily control and won't ask too much questions.
- The prince sees Medea as such a cunning threat, to the point that any correspondence between Psyche and Medea could potentially awaken Psyche to his actual plans for her and derail his ambitions. Therefore he locked up "Psyche" to ensure she'll still remain naive and unknowing by the upcoming party.
- Medea is now aware of the prince's controlling nature, and knows it'll be difficult for her to exercise power as queen given the prince's tendencies. Although she was able to trick him and get out her intended message to Helio, she didn't anticipate the prince would be THAT controlling to the point that any outside correspondence to Medea would be seen as a threat.