Only the third?

[she hums, taking a moment to think about how to best summarize it.]

It's about a religious camp that was turned into a human experimentation facility. The main character is this high-school girl who just moved in with her long-lost sister. But as soon as she does, she starts getting targeted by these people who escaped from that facility.

I haven't gotten too far, but I overheard a friend talking about the plot more than once.