In a post-apocalyptic Earth ravaged by constant warfare with alien invaders known as the Invid, humanity faces yet another challenge as a new and mysterious enemy emerges. The story follows the remnants of the Robotech Expeditionary Force, led by Vince Grant and Marcus “Marc” Rush, who are determined to reclaim their home planet from the Invid. They are aided by Scott Bernard, a survivor of the previous wars, and Ariel, a human-Invid hybrid who strives for peace between their races. As they plan their final assault, they discover that the Invid Regess may not be their only threat, as an ancient alien race and their advanced technology known as the "Haydonites" have returned with insidious intentions.

The plot delves into betrayal, old alliances, and the deep-seated mysteries of Protoculture, a powerful energy source that has been the backbone of Robotechnology. Amidst intense space battles and ground skirmishes, secrets about the past and the nature of the new enemy begin to unravel. As humanity's fate hangs in the balance, the characters must confront their fears, redefine their loyalties, and uncover the truth behind the ongoing galactic conflict. This sets the stage for a climactic showdown, where the survival of Earth and its inhabitants hinges on the success of their daring mission.