Excitement races through Sweetfern Harbor as the famous July boat races near. Brenda Sheffield finds herself busier than ever at Sheffield bed and breakfast. Her place is booked solid, and calls come daily from potential and hopeful customers that have to be turned down.
Brenda has never been as happy as she is now. Detective Mac Rivers asks her to marry him, and she accepts. Her disappointment comes when he wants her to wait to announce the news until after the long weekend is over. She reluctantly agrees.
In the meantime, he suggests they go to Morning Sun coffee shop where the famous three captains are hanging out. They are close friends and fierce competitors and the stars of the race. Scully proves to be boisterous and reigns with bragging rights of winning this race. He jabs his friends in friendly banter, and Captain Pratt joins in. They entertain the crowd that moves closer to their table. Captain Eddy joins in but speaks less words than the other two. He is affable and draws a group of fans, too, but he allows the other two to have their good fun.
Brenda and Mac are invited to tour the new boats crafted by local boat builder Wally Doyle before the races the next day. Brenda is excited to see the inside of a racing boat for the first time in her life.
The next morning, when the captains tell them to go on and take tours by themselves, Mac and Brenda first enter Captain Eddy’s boat. They presume he is inside since he wasn’t with the other two down on Main Street. Shock sets in when they discover Captain Eddy is dead in his cabin. After calling for back-up, they discover signs around the boat that indicate this was not a natural death.
A visiting detective and long-time friend of Mac, Bryce Jones, suddenly becomes the captain of Eddy’s boat. A judge deems the races go forward as planned. It isn’t long into the race when all evidence left on the boat sinks to the bottom of the ocean with the vessel. Bryce barely escapes with his life intact.
With all evidence now gone, Mac enlists Brenda’s help and together they must find out who had a reason to not only kill Captain Eddy but also make sure the crime would not be solved. Plenty of suspects come to their minds: Wally, the boat builder, detective Bryce Jones, now the captain of the dead man’s boat and the two other captains.
It won’t be easy to prove who committed the crime, but Brenda delves into the matter on the side and has her suspicions found to be true when the suspects are called together.