I sense there is an intriguing story here, Nick, but this logline isn't revealing enough to get the juices flowing. There are currently too many questions arising: Where is this set? How come this couple own a secluded castle? Why was it meant to be an idyllic night? Who are the unannounced couple? Did they just turn up or do they live nextdoor? How do they start testing their limits? What are their limits? How does the situation escalate?

Leaving the reader asking too many questions like this out of confusion rather than curiosity isn't going to serve your logline well. It's currently too ambiguous. And while I realise you're keen to keep certain details hidden, you need to give the reader more than what you currently have. We need to clearly gauge a central dramatic question and have some distinct idea of stakes. We should also be able to join the dots and make sense of the information you've given and I do think you can do more here to clarify the scenario.

Do let me know if you'd like any further help with your logline, Nick. Feel free to message me directly.