Will Henry is the assistant to a monstrumologist--someone who studies "life forms generally malevolent to humans and not recognized by science as actual organisms, specifically those considered products of myth and folklore". He's use to the unnatural hours, the demands the doctor makes on his time and his life for the past year since his parents' deaths.
One night, a grave robber brings a strange bundle to the monstrumologist's house with no explanation. The doctor takes one look and is sure they have a big problem on their hands--the bundle turns out to be the body of a young woman with a monstrosity wrapped around her. The monster has no head, a mouth with a lot of teeth in the middle of its chest, and eyes in its shoulders. The doctor is shocked to see such a creature in New England and so begins Will's even more bizarre life hunting monsters and puzzles.
As frightening the concept, especially since they go hunt the monsters in their underground lair, there is a lot of science in this horror tale. Will narrates this story that covers a few days. The story is engrossing and would be most interesting for older teens.