When Michael Humphreys and Sandra Walton are gunned down, detectives don't know who the intended victim was - until they find recordings of phone conversations. S2/Ep5
Dr Margo Prade is shot to death in the parking lot of her own medical practice in Akron, Ohio. Police discover her phone calls were being secretly recorded. S2/Ep4
Michelle Despinasse is shot in her own home and dies from her injuries. In her final moments she made a secret recording that reveals her killer's identity. S2/Ep3
Robin Sowders is brutally beaten in his home and dies from his injuries. After his wife's surprising appearance at the police station, a wiretap reveals the truth. S2/Ep2
Billy Staton and his fiancÂe Leticia Castro vanish. The discovery of a burnt-out car and a shock confession reveal a deceit only a secret recording can untangle. S2/Ep1
When John Riebe is found dead in his home, the investigation quickly focuses on those close to him. Phone calls and voicemails prove key in cracking the case. S1/Ep6
Elderly couple Roy and Angie Woodley are found stabbed to death in their home. Initially believed to be a botched robbery, a vengeful family member becomes a suspect. S1/Ep4
83-year-old grandfather Jack Rains is murdered at his home in Murfreesboro, Tennessee. Rumours emerge of an affair between the victim and a much younger woman. S1/Ep3
Joe Morrissey is brutally killed in an apparent home-invasion robbery. But detectives think the attack was personal and they hunt for suspects - including Joe's wife, Kay. S1/Ep2
When detectives looking for missing mum, Tami Reay, find blood in her car they arrest her husband, Brad. But then they receive a tip, suggesting an entirely new suspect. S1/Ep1