In 1962, investigative reporter Loretta McLaughlin of the Boston Record American embarks on a harrowing journey after uncovering the chilling cases of three older women who were brutally raped and murdered by strangulation in the Boston area. Each victim bore the same haunting signature—stockings tied around their necks in precise bows—suggesting the potential presence of a serial killer lurking in the shadows. The shocking nature of her findings ruffles feathers among Boston law enforcement and her own superiors, who are determined to suppress the story to safeguard the paper's reputation.
When a fourth victim emerges, Loretta teams up with fellow journalist Jean Cole, as they face rampant sexism in a male-dominated newsroom and society. The strain on Loretta's personal life escalates as her long hours take a toll on her marriage, and her family becomes the target of harassment. Amidst these challenges, Loretta coins the infamous moniker "the Boston Strangler" while documenting their findings.
By the following year, tragedy strikes again as a seventh victim, Sophie Clark, is discovered. A neighbor describes a man who could potentially be the murderer, yet this new victim deviates from the established pattern, being considerably younger than the previous ones. As the investigation unfolds, Loretta and Jean realize that the Boston Police Department is mishandling the case, failing to share crucial information with surrounding jurisdictions. They uncover similar murders, including one linked to a man named Paul Dempsey in New York City, that had gone unnoticed.
The plot thickens when Albert DeSalvo, a suspect in this heinous series of murders, is apprehended. A witness is brought in to identify him, but she mistakenly chooses another man, George Nassar. Regardless of this discrepancy, DeSalvo eventually confesses to all 13 murders in 1964. However, due to a lack of physical evidence, he is convicted solely for previous robbery and sexual offenses, receiving a life sentence.
Fast forward to 1965, Loretta discovers through a detective in Ann Arbor, Michigan, that there are six murders there that match the Strangler's methodology. Traveling to Ann Arbor, she investigates and finds that a prime suspect is Daniel Marsh, an ex-boyfriend of one of the Strangler’s victims. Despite being apprehended, Marsh remains uncooperative. In a twist of fate, DeSalvo reaches out to Loretta in 1973, offering to share his version of the events during visiting hours. Tragically, before their meeting can take place, he is fatally stabbed by another inmate.
With the revelation of an anonymous tip, Loretta connects with Harrison, a former patient at Bridgewater State Hospital, who reveals that DeSalvo, Marsh, and Nassar were all housed in the same ward at one point. He alleges that DeSalvo's confession was orchestrated by Marsh and Nassar. In a subsequent prison visit, Nassar denies having coached DeSalvo but admits to hoping for the reward money, throwing doubt on the singular narrative of the Strangler and hinting that multiple killers may exist.
As Loretta and Jean dig deeper, they formulate a compelling theory positing that Paul Dempsey was responsible for the initial six murders before relocating to New York, leading to subsequent copycat killings that targeted much younger victims. The media frenzy surrounding DeSalvo's confessions raised questions about the integrity of the investigative process. Ultimately, Nassar facilitated DeSalvo's representation by high-profile attorney F. Lee Bailey, manipulating the situation to secure a monetary gain and a supposed lucrative book deal for DeSalvo.
The Record American ultimately publishes Loretta and Jean's investigative theory, which contributes to a wider discussion about journalism's role in criminal investigations. In the closing epilogue, Loretta rises to prominence as an award-winning medical reporter at The Boston Globe, while Jean enjoys a flourishing career as a reporter for three decades, maintaining a close friendship with Loretta. In a poignant note, Marsh never faces charges for murder, and Nassar misses out on rewards, remaining incorrectly assumed to linger in prison even as of 2023. The saga reveals that by 2013, DNA evidence linked DeSalvo to the 13th murder, but not to the other twelve, leaving lingering questions about the true identity of the Boston Strangler.
