A struggle to defeat a power-mad clan leader and his sinister brother reaches the crisis point across three worlds in this final installment of The Weir Chronicles. Earth's counterpart, the parallel world of Thrae, has had its core almost entirely drained by Duach leader Aeros and his Pur brother, the Primary. Wracked by earthquakes and volcanoes, Thrae is running out of time. It's up to the three Heirs—Earth-dwelling Ian Black, Thrae's Jaered, and Patrick Langtree, the son of a Duach rebel leader—to work together to save Earth from the same fate. Patrick has only just learned that he is a Weir, a steward of the Earth who wields magical powers. The three Heirs are not alone: Their formidable mothers, Gwynn, Sophenna, and Eve, are on their side, along with Rayne Bevan, a potent Weir (and Ian's star-crossed girlfriend). Rayne is able to drain the magical core of any Weir who touches her. While Ian and Rayne return to Thrae to evacuate the population—and ask the planet's most fearsome creatures for aid—Patrick and Jaered scheme to steal the Primary's hoard of wealth, suspecting he's trying to smuggle it from Earth to a third parallel world, Smara, to start over again in style. As if that's not enough, they realize that to truly defeat Aeros and the Primary, they must break the Curse that keeps their followers, the Pur and the Duach, apart—but how? Duff's (Off Beat: Nine Spins on Song, 2017, etc.) sci-fi series has gotten better with every book, and that's true in this fifth volume, too—she jumps right into the action with a fast-paced escape and rarely lets up. Her characters trot across three globes, with the scenery changing from Paris to Brazil, from the North Pole to the Bermuda Triangle. And she writes intense, propulsive fight scenes—there's an unforgettable image in the climax of a dragon versus a squadron of fighter jets. The stakes are sky high, with planets in the balance, but there are smaller stories too, like Ian and Rayne's romance, stymied from the start by their inability to touch without her sapping his powers. Duff ties these tales up neatly as well. But it's unfortunate that her female characters get short shrift in the end.An action-packed conclusion to a sci-fi series that mostly satisfies.