It's never too late to find where you truly belong. Determined to protect her "vulnerable" mother after a fall, 54-year-old professor Emery Winters returns to Tide's End only to find Vivian and her friends—a group of vibrant seniors who call themselves The Mermaid Society—fighting to save their beloved swimming cove from development. Reconnecting with her coastal roots and childhood sweetheart Jack, the town's harbor master, Emery discovers environmental contamination in the waters and joins the unlikely crusade to protect the area. As Emery applies her scientific expertise to help the Mermaids, she must reconsider where home truly is, what family really means, and whether the career she built far from Tide's End is more important than the unexpected second chance at love and connection she's discovered by the sea.