A cheating husband leaves a meeting from his mistress with a nasty hickey, and him trying to cover it up before his wife gets home becomes a real pain in the neck.

I get that this is probably going to be a vampire film but the “real pain in the neck” doesn’t add anything to the logline. A logline isn’t designed to encourage audiences to see the film the way that a tagline is (“Cheating is a real pain in the neck”) – it’s supposed to give a clear summary of the film in?one sentence that makes someone want to read your screenplay – inciting incident, goal, stakes.

Inciting incident – the hickey – that’s there but if his mistress is actually a vampire then maybe that needs to be included here so the reader knows what sort of film they’re looking at. Something that’s potentially a large part of the film shouldn’t be subtle or require guesswork in the logline.

Is his goal to keep his affair a secret? If so how does the vampire thing fit in? If his goal is not to turn into a vampire then how does his wife fit in. What happens if his wife finds out? What are the stakes?

I think the vampire element needs to be clarified as that’s the bit that is unclear and makes this logline a bit confusing. Once that thread is ironed out I think you’ve got an interesting logline.

Hope this helps.