Ben and crew of The North Star uncover a device emitting a strange sound. Ryn finds shelter in the home of the local folklore expert.
Maddie rushes to Ryn's rescue after she is taken in for questioning. Meanwhile, Ben and Xander return to the deep sea to search for answers, but end up having an unwelcome meeting with an uninvited guest.
Chris escapes the facility as the military enter a state of high alert, but he's not the only one to make it out.
On Murtaugh's first day on the job as interim captain, the wife of a popular businessman is abducted and the squad finds a connection in the case to Rigg's father. Meanwhile, Riggs is left to grapple with his family and work.
As the town of Bristol Cove comes to terms with a recent loss following an incident on the ocean, each of its citizens cope in different ways and it also provides a new education in human emotions for Ryn.
