One stormy night, a homeless dog looking for shelter wanders onto a Coast Guard station in St. Ignace, Michigan. She finds a dry and cozy hiding spot inside a boat's compartment. When the boat launches and heads into the Straits of Mackinac for a search and rescue mission, the frightened dog is still hidden onboard. But when the tireless Coasties are working to save a man overboard, Onyx the dog surprises everyone with her bravery, and she finds more than a home--she finds a purpose.