Major Natalia "Nat" Kerensky establishes a cover operation in Dante City on Planet Dante. One night, unidentified craft enter the airspace and a Stiletto BattleMech touches down — hunting for Foster and the player's MechWarrior. They escape, Nat deploys the new BattleArmor powered armor unit, and hundreds of enemy dropships follow. One is destroyed by the others — a mystery that leads to a crash site survivor: Alera, a space pirate whose jumpship is named the Jezebel.
The fight moves through the city, including an enemy port infiltration using a stolen tank. Scan checkpoints nearly blow the cover and force a breakout alongside allied forces. The full picture eventually surfaces: the aggressors want access to Lostech blueprints and prototypes stored in data cores — specifically the Ragnarok Prototype model from the first game — to mass-produce an unstoppable mechanized army and dominate the Inner Sphere. The final mission deploys the BattleArmor against an unfinished giant BattleMech powered by all five data cores.