When a female book editor visits the home of a horror writer she finds that all of his creations are holding him hostage.

What prompts the editor to visit? Is it that there has been the writer has stopped responding and the reason is because of being held hostage?
Really interesting idea though. I'd like to know more!

When a female book editor visits the home of a horror writer she finds that all of his creations are holding him hostage...and? I would like to know what the Protag is going to do....I think the idea is very creative and it is definitely interesting.

"When a book editor visits a horror writer she realizes that all of his creations are holding him hostage."

So what?

Nobody can really write your logline for you because you're the only one who truly knows your story, but I'm going to give it a go:

"A newly appointed and downtrodden female book editor must rescue her agency's most coveted horror writer when she discovers that his monstrous creations are holding him hostage."

At least this version contains many of the required story elements that need to go into a logline: main character + flaw; goal; antagonist/obstacle; theme; stakes.

Good luck with a rewrite...

Why is the editor being 'female' important? And instead of 'visits' (boring!), put that she goes searching for him, or something... and she has to free him by the time of his book launch.

This is a could-be-good though.

revision of your initial logline
A book editor visits the home of a horror writer where she finds his creations are holding him hostage.

Shorter and more to the point :)

But if you can add a few words as dpg suggests I agree it would be stronger

Who is the protagonist, the book editor or the writer?

Holding the writer hostage for what? What do his literary creations want?

What are the stakes? What happens to the writer if the his literary creations don't get what they want?