A 40-year-old mother disappears from her home in the middle of the night, and police chase multiple leads before coming up empty. Almost a year goes by until they investigate a very unlikely suspect - a high-school neighbor with an affinity for older women. Then, a teenage boy is murdered in his home and detectives believe his campaign against teen gang activity led to his death. But the community is horrified when police arrest one of their "model citizens" for ordering the hit.

A husband and wife are found shot to death on a deserted stretch of highway. Phone records help detectives uncover a murder-for-hire plot that went horribly wrong, and discover that one of their victims is also their prime suspect. Next, when a 20-year-old woman is found murdered near a freeway exit ramp, the residents of San Diego demand justice. But when a trusted police officer is identified for the crime, the community is shaken to its core.

A young boy is killed in the middle of the night, and his own mother is convicted of the crime. Years later, an author investigates a convicted murderer for her upcoming novel, and gets a confession that re-opens that case file and eventually, sets the mother free.

A delivery man guns down an affluent couple, with their only son barely escaping. The investigation reveals a greedy relative with a motive too close to home. And when a recent victim of burglary is found shot to death in her car, the investigation uncovers a killer the victim trusted without question - the police officer who came to her aide.

A judge and his wife are slain in their home, and the suspects range from common criminals to politicians.

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

A wealthy widow is slain, and the victim's records provide the means to find her killer.

When high-ranking oil executive Sidney Reso is kidnapped, an intensive manhunt turns up few clues. Cryptic letters and phone calls send investigators racing to catch the kidnappers, hoping to bring Reso home alive.

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.

A young couple is gunned down on a lover's lane in Georgia; A husband and wife are shot to death in their suburban Chicago home before the killer sets the house on fire.

In rural Wisconsin, a local eccentric is murdered in his home; A serial killer targets the elderly in Lake Elsinore, California.

Detailing the crimes of serial killer Keith Jesperson, also known as the "Happy Face Killer."

A young woman disappears after a flat tire makes her pull over; a man is murdered while minding his neighbor's property.

In 1996, teenaged Joey Martin sneaks out of his bedroom window to watch a comet from a cabin in the woods-and disappears. Despite multiple leads, there is no sign of Joey until 2008 when a young detective uncovers the shocking story of Joey's fate.

In 1985 when welder Danny Paquette is killed in his front yard by a long-distance rifle shot, there is no shortage of suspects. Many people had issues with Danny. But ultimately the solution falls much closer to home than anyone expected.

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.

In 2004, affluent Coral Gables couple, John & Susan Sutton, are attacked at home. Susan doesn't survive. Investigators look at an adulterous business partner and an angry client before cell phone records lead to a shooter with ties to the family.

FBI office manager Melissa Mooney is found murdered in her home. After taking a hard look at several promising suspects, the case goes cold. Two years later, a reexamination of the case leads to an unlikely killer who was hiding in plain sight.

In 1984, terrifying screams pierce the Florida night. A day later, a woman's body is found, stabbed to death. Detective Larry Tosi faces a host of suspects, but when the killer is caught, no one will be more shocked than Tosi himself.

"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.

In 1985, an LA County Sheriff is gunned down in his vehicle. Investigators drill down the slain cop's list of enemies with no results. In 1999, a multi-agency task force shines a new light on the old case, illuminating a culprit who defies belief.

When San Diego Police Officer Kirk Johnson is found shot to death in his service vehicle, evidence points to a fellow law enforcement officer. Detectives reluctantly begin to investigate their own when an astonishing tip leads to an unlikely killer.

Soon after Mardi Gras in Mobile, Alabama, an 18-year-old freshman is found shot to death in the woods behind campus. Detectives take a hard look at several suspects, but thirty years go by before a stunning confession cracks the case.

When tycoon Andrew Kissel is stabbed to death in his Greenwich mansion, detectives are faced with a long list of suspects. Practically everyone who knew the victim has a motive for murder. Ultimately, a secret money trail reveals the guilty party.

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

The 1994 murder of Missy Grubaugh is discussed.

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

The 2002 slaying of a Brunswick, N.Y., couple is investigated.

Investigators in San Diego search for a serial killer after six females are slain in 1990.

The 1997 murder of Henry Caneva and the investigation that nabbed his killers are discussed.

The hunt for burglars who killed a Lafayette, La., man the day after Hurricane Katrina hit the Gulf Coast is chronicled.

The 1992 murder of Angel Ormston and the investigation that nabbed her killer are discussed.

The murders of three women in three Iowa hotels between 1993 and 1997 and the investigation that nabbed the killer are discussed.

The lethal poisoning of a waitress in Florida is investigated.

The murder of a gun advocate in Kentucky and the investigation that nabbed her killer are discussed.

The murder of a man in Maine is connected to a cold case.

The crimes and apprehension of the Texas Bathtub Killer are discussed.

The 1995 death of a Chicago woman whose body was found on a Wisconsin highway is detailed in the Season 4 premiere.

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

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

The 1999 slaying of a young woman in Germantown, Wis., is recalled.

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

Recalling the 1994 murder case of a young mother who was beaten and left in a garbage bin.

The 1991 murder of a young girl in San Diego is investigated.

The 2004 murder and dismemberment of a chef is investigated.

The 1993 strangling death of a young mother in California is probed.

A look at the 2006 shooting death of a young nightclub worker in Scottsdale, Ariz.

A 1993 triple homicide results in the deaths of a Kentucky veterinarian and his family.

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

The 1982 poisoning death of a naval officer is investigated.

The fifth season opens with a case involving a high-school girl who was murdered in 1985.

A Georgia woman is murdered just before Christmas.

A cold case involving a 1988 murder in Sunset Beach, Cal., is investigated.

A 1992 case involving the shooting death of a Maryland businessman is investigated.

A 1990s cold case involving a serial rapist in St. Louis is reopened.

Examining a cold case involving a San Diego postal worker who was murdered in 1972.

The 1992 murder of a church deacon is investigated.

Investigating the 1992 slaying of a Las Vegas woman.

Investigating a 1997 quadruple murder in Bartow, Fla.

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

A former Marine goes missing from his home.

A hotel manager is doused with acid in broad daylight.

A fortuneteller and her daughter are brutally murdered in 2005; a paper trail leads investigators to the culprit.

The Season 6 opener features a serial-rapist case in Reno.

Investigating the 1989 murder of a high-school student.

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

A business traveler is killed in his hotel room.

A 1997 murder in a California town is investigated.

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

The 1980 murder of a California businessman's wife is detailed.

A March 2000 murder in Anchorage is investigated.

The 1980 murder of a Colorado teenager is investigated.

The murder of a Wyoming teenager is investigated.

The murder of a Southern Illinois University student is investigated.

Investigating a daytime robbery at a nightclub in Arlington, Texas, that resulted in an employee's death.

An elderly couple are murdered in their Oregon home.

Shortly before Thanksgiving, a Philadelphia suburb is rocked by the murder of 67-year-old Alice Hufnagle.

In Portsmouth, Va., a 16-year-old ballet dancer is assaulted and murdered in her home, and detectives must investigate her family members as well as her circle of friends.

When a college student is found murdered in his Arlington, Texas, apartment, investigators suspect the kindhearted victim's generosity may have led a killer to his door.

A video tape surfaces after a naval officer is raped and stabbed suggesting the victim may have been silenced to prevent a scandal.

In Fort Pierce, Fla., a tax attorney is found strangled to death, and detectives must scrutinize deadbeat tenants and delinquent clients while hunting for his killer.

When a beloved matriarch is found murdered, her friends and neighbors come under suspicion as detectives investigate the first homicide in the small town of Hubbardston, Mich.

A young Navy wife is found raped and strangled to death in her home near the Mayport Naval Station in Jacksonville, Fla.

An elementary school teacher goes missing after her first day at a new job, and investigators sift through clues to uncover the heartbreaking truth behind her sudden disappearance.

There is no sign of a break-in when 13-year-old Mollie Pittman is attacked and murdered in the Orlando, Fla., home of family friends; it takes investigators 17 years to find out whether she knew her killer.

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 Stockton, Calif., investigators search for 23-year-old Dalene Carlson who has gone missing, then a tractor operator makes a gruesome discovery in a cornfield.

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.

Philadelphia investigators bring to light the obsession that drove a suspect to murder student Deborah Wilson, who was found strangled to death in a university computer laboratory without her shoes and socks.

The murder of a popular young woman in Lancaster County, Pa., is investigated.

The murder of a young woman in her Portland, Ore., apartment is investigated.

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

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

A friendly night out ends in a shallow grave for a beautiful young woman and her killer evades police for decades.

When a well-liked teenage boy is found stabbed to death in his Salt Lake City, UT home, detectives leave no stone unturned in their quest to solve the murder that rocked this normally tranquil town.

Like in one of his old Hollywood westerns, a former actor is gunned down in Yuma, AZ and police chase leads across the Southwest until they finally get their man.

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.

The murder of a California businessman is linked to a contract killer.

When a first-year college co-ed turns up raped and murdered, it takes a freshman cop to beat the odds and catch a killer.

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.

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.