A loving wife and mother shot in the head in broad daylight; the brutal murder is so baffling even seasoned investigators are stumped.

A teenager is murdered; years later and hundreds of miles away, another woman is viciously stabbed; DNA links these two assaults.

A cop and a firefighter are cut down in their prime after suffering excruciating illnesses; a journalist uncovers is a twisted tale of love, passion, and the ultimate betrayal, by a cold-blooded killer.

Peggy Carr and two of her sons are rushed to hospital with extreme pain and nausea; when tested positive for a rare and deadly poison, detectives launch an investigation.

The murder of a young man found beside train tracks and the vanishing of his girlfriend are investigated.

A body is discovered in shallow waters of an old cement quarry, leading detectives to unearth a twisted relationship that ended in murder.

The brutal slaying of a married Toronto couple is investigated, with police turning to a criminal profiler in a bid to crack the case.

The murders of two cab drivers in two days in Austin are investigated, as mounting public pressure is put on authorities to catch the killer.