On the moon, Ronin Hayashi trains to protect the colonies from the inevitable invasion of the machines. While he prepares to stand his ground, Sergeant Tadhg Walsh is planning an escape mission to deliver a weapon to the resistance on Earth.

At Neptune Station, Captain Akira Hayashi and Shadow Squad have returned from a deadly journey into enemy territory where they learn the machines are building an army at an astonishing rate. After continued attempts to contact the Lunar Defense Corps for help, Shadow Squad accepts the hard truth--the LDC isn't coming.

With hope for salvation dwindling, Akira deploys on a desperate mission to find Apeiron, believing only she can stop Doctor Otto Cross from completing his reset of Earth. But Akira soon realizes they need more than just Apeiron. Shadow Squad must somehow reunite with Tadhg and the weapon he carries. Only then can Akira lead the charge against the machines in one last fight for the future of humanity.