[gruundehn]

Another idea: Misunderstood monsters.
A webcomic I enjoy is built around the theme that werewolves and all the other weres are real and have been hiding amongst us for centuries in their normal human guise. It is a funny webcomic but it does have graphic sex so visit it if you wish to see what I'm talking about but be warned. The comic is Peter is the Wolf and the storyline is that Peter accidently creates a new werewolf when he has sex with his girlfriend and the troubles she causes for the pack.
Something similar can be done with the idea of hidden "monsters" trying to keep the secret. The "monsters" are really just normal folks trying to get along.