MARCUS FENIX. WAR HERO. LOYAL SON. TRAITOR. As the Locust Horde advances into one of humanity's last settlements - Ephyra - Marcus does the unthinkable: he abandons his post in a bid to rescue his father, the weapons scientist Adam Fenix. But Adam is lost during an assault on the Fenix mansion, and Ephyra falls to the enemy. As the Coalition of Ordered Governments struggles to defend Sera's surviving humans from the invading "grubs," Marcus faces a court martial. Deserting his post in wartime means the death penalty. But his sentence is commuted to forty years in the COG's most notorious prison - known as the Slab - where a prisoner's life expectancy is less than two years.
In the Slab, there are no rules and no mercy. As Marcus begins this nightmarish day-to-day existence, it will finally be revealed why his sentence was commuted and who intervened to save his life. While his friends and fellow Gears Dom Santiago and Anya Stroud fight to get him released, Marcus must learn to survive in an institution populated by Sera's most dangerous criminals.