Rex faces off against a group of mutant locusts that feed on metal, leaving a path of destruction behind them. However, defeating them is not an easy task as. When they are attacked, the locusts keep dividing through binary fission. As the locusts ra... (more)ge toward China (which holds the Earth's largest metal concentration, Beijing), Providence pulls out all stops to halt their advance. Dr. Holiday comes to odds with White Knight, Six, and Rex as she strongly protests against their "attack first, ask questions later" policy. Finally, the team is forced to consult her for help when the increasing numbers of locusts destroy the Great Wall of China where Providence had made its stand. Eventually, Dr. Holiday synthesizes a concentrated version of a pheromone tag used by the locusts to mark prey, which she sent Rex to gather. While trying to gather the pheromone, Rex almost ends up dead. However, the nanite that Dr. Rylander injected into Rex saved his life, and the only sample left was in his underpants (which had red motorcycles on it). After everyone had a good laugh (Dr. Holiday gave Rex his underwear in front of everyone), Providence sprays it on the locusts, causing them to go berserk and attack (and devour) each other. Finally, Bobo, as revenge for Rex destroying more locusts than him, makes it public that "Providence's Secret Weapon, Underwear, Saves the Day". Rex leaves the Providence briefing room in anger as the story runs on TV, while the other Providence agents continue to laugh at his expense.