Make sure you are crystal clear on the meaning of "theme" -- http://literary-devices.com/content/theme
Since I don't know this title (nor the author!), I don't know, but if you have read the work and understand what "theme" means, you should be able to figure it out. (Hint: There are usually more than one theme in any story/book/poem/play/whatever.)
What is the theme of Nethergrave?
2 answers
I have read this story recently. I have found that the most prominent theme is "You can't trust everyone", but most stories, like this one, have more than one.