Echoes From the Deep: Rick and Marty Lagina send divers deep into the Money Pit in search of a mysterious golden object. (S4, ep 9)
The Mystery of Samuel Ball: The Lagina brothers find important evidence linking an 18th century American slave to the Oak Island mystery. (S4, ep 8)
Motel Massacre: A hotel in Memphis becomes a warzone when a gunfight breaks out, and in Kansas the murder of a two-year-old sparks a manhunt for an eight-year-old killer. (S4, ep 52)
Family Affair: A young woman is brutally murdered - could the killing be personal? (S4, ep 51)
Wolf in Sheep's Clothing: Detectives uncover the shocking truth behind the disappearance of an eight-year-old girl who was abducted close to her home in California. (S4, ep 4)
Blood Trail: A tiny clue leads investigators to the unlikely man behind the murder of 22-year-old Theresa Wesolowski, who was found stabbed 46 times in Germantown in 1999. (S4, ep 3)
The Perfect Suspect: Detectives investigate the mysterious death of a Chicago woman whose body was found dumped on a Wisconsin highway in 1995. (S4, ep 2)
Pure Evil: When the naked body of a Chicago woman is found dumped on a Wisconsin highway, investigators suspect she may be the victim of a lovers' spat which turned deadly. (S4, ep 1)
No Mercy: When a mother of triplets is found dead in her Washington home, detectives piece together her final moments to reveal the surprising identity of her killer. (S4, ep 12)
City Under Siege: Detectives in Arizona investigate whether a 20-year-old woman could be the latest victim of an unstoppable gunman's shooting spree. (S4, ep 11)