The Grace family is back, facing some of their biggest challenges yet as World War II peaks, then reaches its cataclysmic finale.

Based in 1945 Miami, Cloud Haven begins with a flurry of confusion. Orrance, the Conductor of the Train of Thought, turns up at Gracestone, baffled by the disappearance of Annelisa and his beloved dog, Rumpskin. At the same time, Gloomy Gus' daughter shows up, eager to meet the new husband her ghostly father promised her. Ever-changing Shimmera Amandia "becomes" yet another version of herself, throwing off even hard to rattle Sambria, and eventually drawing in a new character, Wise woman Myrrha Emartla, who may or may not be able to help. In Los Alamos, Humboldt continues to toil, distracted from his dreary, deadly work by his best friend, Eagletail, and a young woman named Penny, who finds him inexplicably interesting. He tries hard to forget he knows Jean-Fils and Soto, who are on an inadvisable "mission" in Japan, while worrying about Annelisa, who can't seem to stay put at Gracestone.

Out in California, Perdi tries to manage the Sweet P's and Zolt the Bolt, who aren't as dedicated to their careers as he'd hoped. Hana finds eternal love while Jessie fights Antoine's attempt to reunite her with her estranged mother. Swag tries to find a woman, and does, only to regret it, except for one small happy detail. Nathan finds himself in Possum City, fighting crime with the help of Clarence. Meanwhile, Heartland is in a state of flux, with Amalfus' grip on control slipping. Gracestone is threatened like never before, forcing Henri has to come up with a plan that will allow him and household to live in peace.

Old situations are put to rest while new ones spring up to set the stage for the follow-up series, The Grace Family Chronicles: The Next Generation, set in the Vietnam War era.