A coworker finds Dr. Joseph Sonnier's body face down in the garage of his Texas home. Before long, the list of possible suspects includes the victim's girlfriend, a mysterious stalker, and a long list of jilted ex-lovers.

The shooting of successful paediatric dentist Kendra Hatcher in the gated parking garage of her Dallas condo spurs detectives to unravel a twisted plot as they chase a fugitive who ends up on the FBI's most-wanted list.

A late-night break-in at a Pennsylvania chain restaurant leaves assistant manager Terri Brooks brutally slain; when another female restaurant employee is murdered in a nearby town, detectives fear there's a serial killer on the loose. [also shown as S6:E12]

Holistic doctor Teresa Sievers looks forward to a television career on the horizon until someone bludgeons her to death in her Florida home; a random tip from an out-of-state police chief ultimately brings investigators face-to-face with the killer.

The key to solving the toughest murders lies somewhere in the final 24 hours of a victim's life. Determined investigators must piece together events to reconstruct the timeline, unlock the motive, and ultimately close in on the killer.

In Connecticut, a motorway clean-up crew discovers a suitcase containing the crumpled remains of 24-year-old Valerie Reyes; as the list of potential suspects grows, solving the case may hinge on a portrait of the killer sketched by the victim.

In an affluent New York suburb, killers torture and beat millionaire Ben Novak in his hotel room; detectives soon discover that the businessman had many enemies, but one above all is the sadistic mastermind. [also shown as S6:E17]

A college student's effervescent personality wins him many admirers on his Columbia, Missouri, campus right up until the day of his murder. As a police search for suspects, a tip leads them to someone with a lot to lose.

An enraged killer strikes down 26-year-old Alexandra Ducsay, an aspiring entertainer with a big heart and a blossoming career; slain inside her family's Connecticut home, her attacker uses her own dance trophy to bludgeon her to death. [also shown as S6:E11]

A cold-blooded murder of a 39-year-old woman sends detectives in Oldsmar, Florida on the hunt for a killer, and their only clues are three letters written in blood and a pizza delivery.

A college student is strangled to death in her Bryan, Texas, apartment. Investigators are hard-pressed to find anyone who would want to kill such a bubbly and dynamic woman, but DNA discovered on the scene proves there’s at least one person who wanted to do her harm.

Sixteen-year-old Cassie Jo Stoddart is housesitting in a Pocatello, Idaho, neighborhood. As she watches movies on the couch, Cassie is oblivious to the fact that she's not alone. When she finally realizes that someone evil is lurking, it's far too late.

With two mortal gunshot wounds and tape residue on his wrists and ankles, it's clear 21-year-old Landy Martinez suffered before his death; detectives hope the victim's cell phone provides the critical evidence they need to close in on his killer.

A killer stabs a beloved New Jersey woman 44 times in her home. Investigators have the culprit's DNA, but finding him will require an assist from the FBI, a media blitz and a random tip with details only the murderer would know. [also shown as S6:E9]

A diligent art student lies stabbed to death in bed. The ferociousness of the crime makes little sense considering the quiet co-ed has no known enemies. However, police soon meet someone whose secret hatred for her reveals itself as a night of pure horror.

When newlyweds Joe and Olga Connell are gunned down outside their Wilmington, Del., home, police investigate a sibling rivalry, a business partnership plagued by drugs, and an outlaw motorcycle gang.

On a quiet summer night in 2010, a killer shoots dead a wealthy La Crosse, Wisconsin, couple in their living room. Police look to their financially strapped children for the motive to kill, but a strange discovery may veer them in a whole new direction.

A 42-year-old Russian woman living the American dream in Texas is savagely gunned down in her garage. As investigators work the case, the list of suspects includes her controlling ex-husband, her boyfriend, an obsessive admirer, and a generous mentor.

A St. Charles, Missouri, businessman dies violently at work, and police suspect it was a business deal gone bad. Then they discover several insurance policies plus a secret double life, and their investigation veers into a whole different lane.

Niagara Falls detectives find 72-year-old real estate agent Bruce Firman bludgeoned to death with a pipe wrench in the home he shares with his estranged soon-to-be ex-wife; Bruce was also a serial monogamist with a long list of jilted ex-lovers. [also shown as S6:E10]

A car explosion outside a Tucson country club leaves a business tycoon dead. Detectives determine the killer detonated the homemade bomb at close range, and the list of suspects soon includes mobsters, defrauded investors, and the victim's ex-wife.

When a 42-year-old woman is strangled to death and posed in an unusual way in her bedroom, detectives are on the hunt for someone who would have wanted to humiliate her after murdering her. A hidden 911 call turns the case on its head.

A Tennessee college student returns to campus to find her friend and roommate Heather Maples viciously strangled in her bed. The outgoing co-ed has many friends, but police fear that on August 7, 2015, one of those pals turns out to be her worst enemy.

A 36-year-old woman lies strangled to death in her own home. Clues at the scene indicate she knew her killer well enough to let them in and that the resulting murder was spontaneous. Now, police race to discover who could want this mother dead and why.

A 911 call from a worried ex-boyfriend sends police to the Powder Springs, Georgia, home of Danielle Marshall. Once there, they find her shot dead in the kitchen. As the suspects multiply, it takes some police ingenuity to nab the killer.