A routine mission in Cuban waters to retrieve a hidden. key code from a sunken Soviet submarine quickly changes, course when Cuban officials are tipped off. It turns out that Nadia, the beautiful stranger who saves Chapel from being discovered, is actually a Russian agent, and her intel is shocking. Hidden during the Cold War, a forgotten Russian supercomputer controls hundreds of nuclear missiles, all aimed at the United States. Just one fail-safe error and America will be obliterated. To disarm Hydra before it plunges the United State into nuclear winter, Nadia and Chapel must travel across Eastern Europe and infiltrate a secret base hidden deep in the steppes of Central Asia. But as these uneasy allies discover, not everyone wants the weapon out of commission.