a boy takes a picture of the animorphs while they are demorphing in an alley after a mission. they track the boy down and decide to keep watch on him. when they go to cassie's barn to reconvene, the helmacrons show up and demand the morphing cube, because they need it to charge their ship. in the ensuing battle, the helmacrons leave the ship and enter marco's nose. the animorphs decide to use the helmacron ship to shrink themselves so they can follow the helmacrons and stop them from killing marco from the inside. when they shrink, they realize they are too small to hear the speech of full-size humans, which didn't happen the last time they were shrunk. when they catch up to the helmacrons inside marco's nose, they notice that they have been shrunk to 1/100th the size of the helmacrons, who tweaked the shrinking device before they left their ship, knowing that the animorphs would shrink themselves so they could go after them.