The Girl and the Last Sleepover

A shy outcast girl from the rural outskirts of a small town is invited to a girls' sleepover with two other girls.
In the middle of the night a horrific fire erupted.
By the time emergency services arrived, it was too late.
Investigators assumed the parents, their daughter, and her 2 friends died in the home.
But only one body was uncovered, the mother's... For years FBI Agent Emma Griffin was largely a lone wolf.
She insulated herself from the rest of the world. With very few exceptions.
Now, that has all changed. Opening herself has given her a chosen family she loves. Working with her cousin Dean has always made her happy, and now she can help someone find a piece of their family that disappeared years ago.
An FBI agent who went undercover and never surfaced.
As they dig deeper into his disappearance, they find a potential connection of that case with the mystery of the 3 girls.
But as bodies connected to the case turn up in odd locations.
Emma struggles to make sense of what happened the night of their last sleepover.