At Christmastime, Russel Douglas is found shot to death in his car on a deserted road on Whidbey Island north of Seattle; it's the start of a case that will take a decade to solve and leave many with lingering questions.

Forty-two-year-old Miami mother Raquel Calderin vanishes without a trace on her way home from work in 2012; the investigation into disappearance leads detectives deep into a disturbing family picture, and the truth will haunt them for years to come.

A freak car accident brings a Belgian honeymoon to a tragic end, and the investigation leads police down a rabbit hole and culminates in an international manhunt for a killer.

When a woman is murdered in Milwaukee, her sons describe a masked man with a ponytail fleeing from the home, and police investigate the victim's rancorous ex-husband and a neighbor who claims his gun was stolen.

Atlanta preschool teacher Julie Love goes missing just a week after getting engaged to boyfriend Mark; detectives find numerous suspects in the teacher's disappearance, but the truth turns out to be far worse than they could have imagined.

The body of 20-year-old student Sandra Bonaventure is discovered in a garbage bag on a sidewalk in New York City; the trail of clues lead to a cold-hearted killer who possesses an astonishing talent for deception.

An intruder shoots Daniel Ott dead with a shotgun in a stunning case of mistaken identity that leads investigators into the heart of one of the most dangerous criminal rings in the country.

Pro football player Sean Taylor is shot dead by an intruder in his Miami home.

Hollywood golden boy Gavin Smith, a 20th Century Fox executive and former star UCLA basketball player, goes missing; for years, his family and detectives search tirelessly for answers, but a group of heartless characters hold fast to their secrets.

Motivational speaker Jeffrey Locker, 52, is found stabbed to death in East Harlem, N.Y.; at first, detectives suspect Locker was in the wrong place at the wrong time, then they learn the truth is far more complex and shocking.

University of Miami football player Marlin Barnes and his friend, Timwanika Lumpkins, are beaten to death in Barnes' apartment; as detectives search for the vicious killer, the crime sends shock waves through the campus and community.

After 39-year-old Dawn Viens goes missing, her chef husband, David, reports she ran away to escape her problems; the investigation leads detectives to an unexpected killer who disposed of Viens' body in an unimaginable way.

In Bronx, N.Y., police investigate the murder of 20-year-old Kimberly Antonakos who was set ablaze while still alive.

Film director Adrienne Shelly is discovered hanging by a bed sheet from the shower rod in her bathroom; while Shelly's death looks like a suicide, her husband insists it was murder, and detectives start to believe him.

When Robert Schwartz, a father of three, dies in a brutal murder in his own home made to look like a ritualistic killing, the investigation uncovers a killer much closer to home.

A car races up to the emergency room doors at a Mount Kisco, N.Y., hospital; driver Carlos Perez-Olivo has been shot in his side, while wife Peggy has been shot in the head; investigators must determine what horror has befallen this couple.

Ann Anastasi returns home from shopping to find her husband, Anthony, lifeless in bed, a gun beside him; police soon find a second victim, Jacqueline Riggs, in the basement; later, they discover a dark tale of love, lust and violence.

On Long Island, a man pulls into a gas station claiming his wife has been shot dead by a motorist on the highway, but he's foggy on the details.

Peter Theriault, 51, has never missed a day of work in nearly 30 years, then he fails to arrive for his shift at a car plant in Commerce City, Calif.; his family and friends immediately suspect that something is very wrong.

Twenty-six-year-old car dealer Christopher O'Brien takes a stranger for a test drive and never returns; investigators wonder whether O'Brien's criminal past has caught up with him.

After New York City fashion photographer Joel Schoenfeld is shot dead in his Greenwich Village studio, detectives uncover a dark secret and a twisted tale of revenge.

Some of the world's most notorious murders are the subject of "It Takes a Killer," which investigates the crimes from the perspective of the killers, trying to get inside their minds and determine their motives. Leading homicide investigators and experts from such agencies as the FBI and Scotland Yard take a look at the evidence pulled from crime scenes and profile the killer's behavior to try to piece together the details of each murder, explaining when, why and how each criminal committed the crime. For the wannabe detectives watching the show, the experts also reveal how the crime was solved -- which often requires authorities to think like a killer.