The freedom fighters have finally started their journey across the mountains, but have found no way to get past the Invid stronghold at its center. They opt instead to go through it, with Scott and Rand formulating a daring plan to destroy the fortress: Rand and Annie will infiltrate the fortress after most of the Invid troops leave on patrol, and then knock out the protoculture sensor. Scott and the others will then be able to use the fighters to destroy the base. Once inside, they happen across what looks like a giant brain: an extension of the Invid Regis that runs the fortress. They realize that the brain-like creature is the protoculture sensor they’ve been looking for. When they destroy it, there are two unforeseen consequences: Marlene once again experiences one of her mysterious headaches and, in the fortress, the shattered pieces of the brain attack and envelop Rand and Annie, threatening to suffocate them., The Invid are attacked at an abandoned Robotech fortress used as a research laboratory and military base.