The key to solving the toughest murder cases lies somewhere within the final 24 hours of the victim's life. Following investigators as they piece together events.
Dr Joseph Sonnier's body is found in the garage of his Texas home. Before long, the list of suspects includes his partner, a stalker and jilted ex-lovers. (S4, ep 1)
A successful dentist is gunned down in the gated garage of her condo and detectives must unravel a twisted plot to chase down a fugitive at large. (S4, ep 2)
When a holistic doctor with a burgeoning TV career is bludgeoned to death inside her home, it's a random tip that leads to justice being served. (S4, ep 3)
For Connecticut police, solving Anna Lisa Raymundo's murder hinges on a mysterious 911 caller. An investigation from a neighbouring state breaks open the case. (S4, ep 4)
Slaying in St Petersburg: With gunshot wounds and tape residue on his body, it's clear Landy Martinez was tortured before his death. Police believe a phone may crack the case. (S4, ep 5)
A suitcase containing the remains of Valerie Reyes is found. Solving the case may hinge on a portrait of the killer sketched by the victim's own hand. (S4, ep 6)
A public health nurse in Alaska disappears and police get a major break from a terrified neighbour. Investigators race against the clock to reach the truth. (S4, ep 7)
A single mother's body is found in a snowbank and the evidence points to a fugitive fiance. A second murder sparks fears of a potential serial killer. (S4, ep 8)
A much-loved New Jersey woman is stabbed 44 times in her home. Investigators uncover the truth after a random tip with details only the murderer would know. (S4, ep 9)
Bruce Firman is found bludgeoned to death with a pipe wrench in his own home. Investigators uncover a trail of jilted ex-lovers before finding the killer. (S4, ep 10)
Alexandra Ducsay is bludgeoned to death inside her Connecticut home with her own dance trophy. Police battle to reach the truth and bring the killer to justice. (S4, ep 11)
A break-in leaves a restaurant assistant manager dead, and when a similar murder happens nearby, detectives fear there's a serial killer on the loose. (S4, ep 12)
Follow US detectives as they reconstruct murder victims' catastrophic final hours to help catch their killers. (S4, ep 13)