For more than a year, investigators discovered human remains along a stretch of Ocean Parkway in Suffolk County, Long Island. The victims who could be identified were young women, many from the New York City area, who had worked in the sex industry and gone missing — in some cases, more than a decade before they were found. It became clear that a serial killer was targeting this particularly vulnerable population, but for more than 13 years, the case languished. In 2023, though, a man suspected of being the “Long Island Serial Killer” was finally apprehended.

Gone Girls: The Long Island Serial Killer, a three-episode documentary series which premiered on March 31, delves into the lengthy investigation that culminated in a much-awaited arrest. It also explores the stigma surrounding the victims’ line of work, which may have contributed to the inquiry’s frustratingly slow pace.

“These family members were never going...