The salty breeze of Plymouth Harbor carries whispers of a dark past. Freelance photographer Kat MacIntyre is ready for a relaxing summer capturing whales on camera, but a shocking discovery aboard a local tour boat changes everything. Teamed with her intuitive rescue dog, Dash, and guided by mysterious insights from her ancestor Quinn "Mac" MacIntyre, Kat uncovers a web of rivalry and secrets stretching back centuries.

As tourists flock to Plymouth, the race is on to catch a cunning killer. Can Kat piece together the clues before the tide turns against her?