Pressed into service when World War II breaks out in the Pacific, the US Walker—a Great War-era destroyer—finds itself retreating from pursuing Japanese battleships. Its captain, Lieutenant Commander Matthew Patrick Reddy, desperately leads the Walker into a squall, hoping it will give them cover—only to emerge into an alternate world. A world where two species have evolved: the cat-like Lemurians and the reptilian Griks, and they are at war.

With its power and weaponry, the Walker's very existence could alter the balance of power. And for Reddy and his crew, who have the means to turn a primitive war into a genocidal Armageddon, one thing becomes clear. They must determine whose side they're on. Because whichever species they choose is the winner.