Well, since it's Agatha Christie-esque, I do think it's one of the guests. Olivia would seem too obvious however. It could be Olivia and Nick though.
If it's Raoul I'll die laughing.
The sentence structure isn't terrible, nor is it choppy at all. However I've been undergoing long periods of studyig english sentence structure to go from English to Honors English and I find myself mentally editing every setence so it flows better, or checking some comma mistake.
Of course I'm not following them in my post...
Also, I was a bit suprised when you said foreign language. When I read your stories, they seemed to come from a natural. Someone who has a nack for putting words together. It could come from the fact that you do talk another language and have a unique way of wording.
So yes, Nick and Olivia....