In this Shark Week whodunnit, a rare surge of highly aggressive shark attacks hit a tight-knit community off Australia's southern coast, prompting marine biologist Dr. Riley Elliott to find and tag the oceanic suspects. But when he discovers this could be a new, elusive population of sharks, he builds the world's first "chum island" to lure them in and uncover if they are the ones responsible for the attacks.

Phil Torres and Heather Amaro travel 5,000 miles west of the U.S. to the remote Marshall Islands, home to the world's largest shark sanctuary, where apex predators are exhibiting highly aggressive behaviors and erratic swimming patterns. Between 1946 and 1958, the United States military detonated 67 nuclear bombs around the island, raising questions about their lasting impact on marine life. Now, the team dives into these dangerous waters to investigate reports of "mutant" sharks and uncover whether atomic blasts could be to blame.

Global explorer Josh Gates travels back in time and dives into the history behind some of the world's most infamous shark encounters, from the earliest known shark attack to the mystery surrounding the shark feeding frenzy faced by sailors following the sinking of the USS Indianapolis in remote waters. He also investigates the legendary "Stronsay Beast," a mysterious creature that washed ashore in Scotland in 1808, long thought to be a sea monster. But could it in fact be the remains of a massive shark?