12-year-old Linnea Vulkane is looking forward to a long, lazy summer on Grandpa Heph's farm, watching newborn kittens grow up and helping out with chores. That all goes out the window the night Mars, god of war, demands her grandfather abandon her and return to Olympus for the brewing war. Now Old Vulcan is racing around the world and across higher planes with Sehkmet to gather allies, leaving Linn and an old immortal friend to protect the farm and the very special litter. But even the best wards won't last forever, and when the farm goes up in flames, she is on the run with a daypack, a strange horse, a sword, and an armful of kittens. Linn needs to grow up fast and master her powers, before the war finds the unlikely refugees...

Linnea Vulkane has grown up since the summer of Vulcan's Kittens. Sanctuary, the refuge of immortals on an Hawaiian island, is boring. When the opportunity for an adventure arises, she jumps right into it, only realizing too late the water may be over her head. Literally, as she is embroiled in the affairs of the sea god Manannan Mac'Lir. Merrick Swift has a secret he's ashamed of. When he meets Linnea and her best friend, he doesn't like her. She's bossy, stuck up… and oddly accepting of his wolf heritage. Like her or not, he must do his duty and keep her alive. The children of the myths are being plunged into the whirlpool of immortal politics, intrigue, goblin wars, and they might be the only ones who can save a world.