Underground in the white hall, Roy titters at Edward's choice of company now that he has joined up with Human Chimeras and Scar, but when it becomes apparent that Fullmetal's gang requires the Colonel's help against the rising horde of Mannequin Soldiers, the Flame Alchemist produces a torrent of fire that incinerates the lot of them in a single blow. Just above them, May continues her attempt to flee from the restored Envy, heading closer to the source of the foul energy flow, but their scuffle causes a tunnel collapse and plunges them both directly into the midst of Edward's group. As Scar scolds the young girl for returning to Central instead of heading back to Xing, Envy interjects, jeering the group and attempting to cause discord between Scar and the State Alchemists, as he finds human struggles amusing, but his taunts fall on deaf ears. Mustang, aware of Envy's identity and shape-changing abilities, remarks that he finds the foolish struggles of the Homunculi far more amusing before demanding of Envy the name of Maes Hughes' murderer. The Homunculus tries to pin it on Ross, but Mustang declares that he was always aware of Maria's innocence and asks again. Laughing, Envy finally admits that he himself was the one to take the Lt. Colonel's life, but when Roy expresses his skepticism that Maes could have been killed by such an idiot, Envy reveals his trick and transforms once again to resemble Hughes' wife Gracia. Finally convinced and painfully furious, Roy prepares his two Flame Alchemy gloves and swears that the first thing he'll burn away is Envy's tongue.

Roy's features visibly warped by rage, he asks Scar and Ed to let him take down Envy on his own while they go on ahead. Envy attempts to stop the others from going any further, but with a burst of flame, Mustang remarks that he alone will be the Homunculus' opponent. Worried, Edward asks Hawkeye if she and the Colonel will be all right on their own and, with her pistol drawn, she assures him that they'll manage and the others continue toward Father's inner sanctum. However, Edward remarks that the question of the Colonel's safety was not what was distressing him. Envy transforms to his massive original form in preparation for battle, but - now with an even larger target - Roy wastes no time in sending out alternating blows that boil the Homunculus' eyes and bathe his monstrous body in flame. Remembering that he now faces the man who burned Lust to ash, Envy creates a diversion, slips back to his human shape and flees from the hall. As Roy desperately gives chase, he orders the apprehensive Lt. Hawkeye to stay behind.

Led by May toward the source of the flow, the others press on, but Edward hesitates and cast a meaningful glance at Scar. The Ishvalan recognizes at once that Edward is still concerned about Roy and remarks that he knows what it's like to become consumed by revenge, confirming that the path upon which Mustang has embarked will burn his heart away. Back through the tunnels, the burnt and terrified Envy hides from his pursuer and attempts to use his favorite trick as Mustang approaches - changing form to resemble Hughes. But Roy, even more incensed, wastes no time torching the impostor and recommences his furious onslaught. Concerned by the sounds of their battle, Hawkeye disobeys her order and plunges into the dark tunnels ahead in pursuit of her commander. Desperate to escape, Envy dives through a pit, causing Roy to begin searching for his quarry again. However, the temporarily unengaged Homunculus spies Riza wandering through the tunnels and sees a sinister opportunity. Moments later, Hawkeye and Mustang encounter each other in the maze-like tunnels and each lower their weapons as the Colonel informs the Lieutenant that he has lost Envy's trail and orders her to stick close to him. She complies, but as they continue on in search of the Flame Alchemist's prey, Hawkeye raises her pistol again and takes aim at the back of Mustang's head.