The murders of three Arlington, Texas, teenagers in 1985 and the subsequent homicide investigation are discussed.

Season 3 premiere. An attack on a Pennsylvania family that left only one survivor is discussed.

A hotel manager is doused with acid in broad daylight.

In 1988, a 9-year-old girl goes missing in Great Falls, Mont.; the case goes cold until a chance encounter at a bus stop breathes new life into the investigation and leads to the horrifying truth behind the girl's disappearance.

"Went 2 Talk 2 Rob" are the last words 15-year-old Becky Stowe writes before she slips out, never to be seen again. Did she run away or did her boyfriend Rob make her disappear? Two years go by before the truth about Becky is finally revealed.

Investigating the 1992 slaying of a Las Vegas woman.

In La Jolla, Calif., telemarketing manager David Stevens' charred body is found in his burned-out car, and detectives encounter a rogue's gallery of suspects while looking for his killer.

In Arkansas, three women are murdered over the course of three years.

A Kentucky woman is found dead in the trunk of her car.

A series of California fires puts investigators on the hunt for a serial arsonist. After years of dogged investigation, an unpopular theory points to a disturbing culprit.

The 1995 murder of an 8-year-old girl sparks a manhunt for her killer.

The 1985 murders of a young military wife and two of her daughters are investigated.

The 2004 murder and dismemberment of a chef is investigated.

The murder of an 8-year-old boy sparks a decades-long investigation.

After a young girl describes her mother's killer as being a ninja, police attempt to work out the truth behind the child's description as they put the murderer behind bars.

The police manage to track down the killer of a disabled Denver woman and they attempt to establish whether or not she was killed for money or if there was a more personal motive for her death.

A serial killer on the loose in Spokane prompts investigators to take a new look at an old clue.

The 1982 poisoning death of a naval officer is investigated.

The strangulation death of an 8-year-old girl in Ocean Shores, Wash., is investigated.

The leading advocate for the controversial science of cold fusion is beaten to death and investigators run the full gamut of suspects, from corporate executives to drug-crazed burglars, to find his killer.

When 10-year-old Katie Collman is murdered in a small Indiana town, a shocking confession catapults this crime into national news. Was Katie murdered to keep her quiet about something she saw? An unusual clue leads investigators to the conclusion.

The 2001 strangling death of a mother of triplets in Puyallup, Wash., is investigated.

A mother's tireless pursuit for justice in her son's murder leads investigators to find a crucial clue.

The investigation into the murder of a young North Carolina woman is recounted.

The killer of a Santa Monica art teacher remains at large for years as police use every trick in their arsenal to finally hunt him down.