The Dolphins of Laurentum

In the fifth volume of the popular series of historical mysteries, a ragged stranger and the prospect of losing her family's fortune lead Flavia Gemina and her friends, Jonathan, Lupus, and Nubia to a seaside villa. There, they discover a shipwreck and sunken treasure — and that someone else is after the treasure, too. As they solve the riddle of the wreck, the four friends also stumble across the terrible mystery of Lupus's past.