Ben finds a strange sound-emitting device on the North Star that could potentially lead him to Chris.
The military facility is on high alert, and while Chris manages to escape, he is not the only one to make it out.
Ben investigates some suspicious overfishing; Decker increases his efforts to find his escaped mermaid and shows the true extent of his influence.
Maddie rushes to Ryn's rescue after she is taken in for questioning. Ben and Xander return to the deep sea in search of answers, but are met by an uninvited guest.
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.