It’s springtime in Martha’s Vineyard, and Priscilla attends the annual Lambapalooza festival going on at Derry Wilson’s farm. When a cryptic message is sheared into Derry’s prize sheep Sally, just as the animal is about to go into auction, Priscilla—aided by Gerald and her cousins—sets out to find out who’s behind the prank. Is it the animal activist who pickets the event each year, the rival farmers with a history of conflict with Derry, or someone else intent on mischief? Meanwhile, something is troubling Gerald, and Priscilla finds it almost as much of a mystery as the sabotaged sheep. Can she uncover answers to both puzzling mysteries?