 Tris takes one of the pirate's "boomstones"—a hard sphere containing gunpowder—with her winds and sends it away.Briar and Rosethorn take seeds of thorny plants and grow them quickly and thickly along the cove to capture and kill the pirates.When all the adults leave to help defend Winding Circle, Tris practices zapping targets with her lightning and the help of Sandry, Daja, and Tris.