This story is told in two timelines. In one, we follow Jamie and Emma, two teenage sisters who switch babysitting job at the last minute. Jamie, who was supposed to babysit, went to a senior party, and Emma, who covered for Jamie became a victim of a vicious attack that left her alive, but with cognitive issues.
The second timeline takes us to almost 20 years later, when Jamie is forced to move back to her hometown to take care of Emma and new set of attacks start again.
This is a very slow burn mystery/thriller. While I enjoyed the writing (this is my first book by Nancy Bush, but it wouldn't be the last), there were parts of the story that were extremely repetitive and boring. I mean, at some point, we were asking the same question for literally 50 pages or so (and still not getting the answer).