The discovery of four women's bodies on Gilgo Beach was just the beginning. But who is the Long Island Serial Killer? Investigators uncover multiple suspects and shocking theories, as they race to capture this prolific killer before he strikes again.

[The Keddie Murders] A mother and three teens are murdered in the remote town of Keddie, California. Despite a trail of suspects and illicit activity, no one was ever brought to justice. But recently discovered evidence may be the key to finally cracking case.

[Los Angeles Serial Killer] A lone survivor is the only witness who can help police track down a serial killer known as the Grim Sleeper, who preys on women in South Central Los Angeles. After decades of searching, police hone in on an unlikely suspect.

[Mystery in Texas] In 1995, 16-year-old Adrianne Jones is found shot to death in Grand Prairie, Texas. A model student and athlete, there seems to be no reason for her death. Police investigate boyfriends, neighbors and local troublemakers, but don't have any strong suspects. The case grows cold, until nine months later when a game of Truth-or-Dare leads to a startling confession and an over-achieving relationship that went murderously awry.

When a vivacious young escort, Shannan Gilbert, vanishes on Long Island's south shore in 2010, her disappearance leads police to discover the bodies of ten other victims dumped by a serial killer.

[A Ghastly Discovery] In 2012, hikers in Los Angeles' Hollywood Hills discover the severed head of Hervey Medellin, a retired flight clerk. The cast of suspects includes former lovers, drug cartels and a murderous porn star, in a tale of lust, greed and butchery.

[Murder in Alaska] In 2004, the small town of Craig, Alaska is shocked when police discover the charred body of beloved mother and wife Lauri Waterman. People have no idea who would want to kill her, until an unlikely witness reveals a sordid story of secrets and lies.

[Gone Without a Trace] In 2011, a 10-month-old baby girl goes missing from her home in Kansas City. The family fears she's been kidnapped by a drifter, only to be accused by the police of being responsible for her disappearance.

[Murder by the Book] On June 12, 1991, outgoing Jackie Galloway is found strangled and bound with ritualistic knots. Police investigate suspects in her inner circle but are shocked when a chance encounter with a prowler leads them to discover the murderer is a budding serial killer.

[20-Year Murder Mystery] Six-year-old beauty queen JonBenét Ramsey is found murdered in her Boulder, Colorado home in 1996. Investigators try to unravel if she was killed in a kidnapping-gone-wrong, by a home intruder or by one of her own family.

An army surgeon, Jeffrey MacDonald, is the lone survivor of a brutal 1970 home invasion that claims the lives of his wife and daughters. But authorities doubt his story of murderous hippies and believe MacDonald is the culprit.