In this famous Old English epic poem it's Monsters vs. Humans. Grendel (and Grendel's mom) are wreaking havoc on a bunch of merry mead drinkers in their castle.
Luckily Beowulf shows up to show these animalistic creatures who's boss. Beowulf defeats the critters, and life goes back to normal—but now with even firmer lines drawn between what is human and what isn't.