When Darlene Roberts pulled over to help a stranded motorist on a lonely dirt road in Alabama in April 2006, her Good Samaritan act would cost her life. The next day her body was found lying face down in a nearby pond, blasted by a shotgun. As investigators sought answers, they realised this was not a random kill. They started to question Darlene's husband Vernon, and his ex-wife Barbara Ann Roberts. What detectives gradually unravelled was a bungled kidnapping plot involving multimillionaire neurosurgeon Dr Robert John Scheiss III. Location - Rome, Georgia and Conyers, Georgia. Biotech executive and San Diego multimillionaire John Watson was due to pitch a major presentation to a board meeting in June 2010. When the reliable businessman failed to show, a colleague discovered Watson dead in his La Jolla home. At first, police believed it was natural causes, until Watson's friends pushed for an autopsy. It was a revelation - Watson had been tasered and strangled. Then someone claiming to be John Watson attempted to transfer nine million dollars from one of his bank accounts. The ensuing investigation uncovered a killer driven by envy, avarice and delusions of grandeur, who'd spent many months methodically plotting the malicious murder of his friend. Location - La Jolla, California.