ARC provided by NetGalley in exchange for an honest review.

I have been a fan of Ellen Marie Wiseman's work since I read "What She Left Behind". As an institutional historian, I look for books in which it is clear the author has done their research but manages to build a story that isn't weighed down by that research. "The Lost Girls of Willowbrook" is one such book. Wiseman deftly weaves together the history of institutional care and the history of Willowbrook itself which serves as a backdrop for an incredible mystery that, sadly, is an accurate echo of real-life circumstances in many of these institutions.

For the past six years, Sage Winters has believed that her twin sister Rosemary died of pneumonia. Instead, she discovers that Rosemary was in fact committed to Willowbrook and is now missing. Concerned about her sister, Sage hops a bus to Willowbrook to join in the search for Rosemary but when she arrives, she is immediately mistaken for her sister and taken away to the wards where she witnesses unspeakable horrors, neglect, and abuse at the hands of the attendants as well as the so-called doctors. The only person who seems to believe that she's Sage and not Rosemary is Eddie King, the janitor she sees every day cleaning the overcrowded day room. Eddie engineers some time alone for the two of them and tells her he knew right away that she wasn't Rosemary and he was willing to do whatever he could to help her get out of Willowbrook and find out what actually happened to her sister.

What follows is a series of unexpected twists and turns that take the reader even deeper into the bowels of the institution as Sage fights for her freedom and justice for not only her sister, but for all the lost girls of Willowbrook.