In the pulverized ruins of eastern Ukraine, the battle for Chasiv Yar is the focal point of the entire war. For the Ukrainian defenders, it is the last door protecting the country's heartland; for the relentless Russian army, it is the gateway to total victory. At the center of this inferno is Captain Ivan Tkachuk, a battle-weary officer tasked with holding the city’s most critical sector: the Kanal microdistrict.

Haunted by past battles and carrying a tremor from a shell that landed too close , Ivan is given command of the last reinforcements—a handful of terrified new soldiers who still believe in the neat lines on a map. But Ivan knows the truth: the maps are a fantasy, and command’s strategies are designed by men in clean bunkers far from the slaughter. Faced with an overwhelming Russian advantage in artillery and the terrifying, building-erasing power of massive glide bombs, Ivan must teach his men a new kind of war. He forces them to abandon protocol, to carve "mouse holes" through concrete walls, and to fight like rats in a maze of their own making, all to survive the onslaught.

When a shocking discovery reveals the Russians are executing an audacious flanking maneuver that could collapse the entire front , Ivan’s warnings to high command are dismissed as the ravings of a compromised officer. Abandoned, outgunned, and with the enemy closing in from all sides, Ivan learns the only thing worth fighting for is the man next to you. Now, with his position designated a sacrifice zone and his men ordered to hold the line to the last, he must make an impossible choice—one that will cost more than he can ever imagine and seal the fate of the Chasiv Yar door forever.