Lost Girls Ending Explained: Who was the k*ller?

Lost Girls is a film in the mystery drama genre that was released on Netflix on March 13, 2020. Written by Michael Werwie, the film is directed by Liz Garbus. It's adapted from Robert Kolker's 2013 non-fiction book Lost Girls: An Unsolved American Mystery. Prior to its release, the film had its premiere at the 2020 Sundance Film Festival. Here's the official synopsis:

When Mari Gilbert’s daughter disappears, police inaction drives her own investigation into the gated Long Island community where Shannan was last seen. Her search brings attention to over a dozen murdered prostitutes.

Let us take a look at its ending.

What is the plot of Lost Girls?

Lost Girls takes its leaf from the real-life incident involving the killing of several prostitutes in Long Island, New York, between 1993 and 2011. In 2023, a man named Rex Heuermann was charged with the murder of several women from that time. It focuses on Mari Gilbert (played by Amy Ryan), who is looking for her daughter Shannan Gilbert, who has gone missing. She asks the local authorities to look for her, and eventually the bodies of several prostitutes are discovered in the South Shore region.

How does Lost Girls end?

Lost Girls reveals that Dr. Peter Hackett (played by Reed Birney) was the main culprit behind the killings. He was also getting the help of his wife in these crimes. But Hackett uses one artificial leg, which rules out his involvement. But his neighbor Joe Scalise (Kevin Corrigan) saw him hiding one of the bodies. Mari had been following him for a while and told Dormer that he was the killer of her daughter. Towards the end of the film, the cops investigate a swamp area that is right behind Peter's house. That is where Shannan's body is found. This establishes that Hackett was the killer.

The film showcases the authorities' reluctance to question Hackett for his link with the girl's disappearance. It boils down to two things: the victim being a prostitute (and the general disinterest in them because of their background) and Hackett's reputation as a doctor. The film leaves certain threads unanswered, including the question of whether the neighbors knew of his involvement in the m*rders. Towards the very end, as the cops discover Shannan's body, her mother speaks about how her daughter did not get the importance she should have received.

Through the real-life incident and its inspirations, Lost Girls talks about the plight of prostitutes in our society. The general sentiment is that no one cares about them, and even authorities are unbothered if something happens to them.

In a Collider interview, Amy Ryan spoke about the character of Mari Gilbert.

"Mari had an extremely hard life. She was a single parent who worked a few jobs, and she made really hard decisions with some of her parenting choices, which I'm sure, at the time, she believed were her best choices. What I love about the film is, she's trying to forgive herself and make things right. She believes she was a horrible mother, but every day, there are so many opportunities to fail. You try to raise these young human beings into stellar people, and it's hard, and Mari was doing her best. Having not met her, but understanding her circumstance and the obstacles she faced, she was doing her best."

What do you think of Lost Girls' ending?