Applegate Katherine Alice. The Animorphs 42. The Journey

The book is known to have been ghostwritten by Emily Costello.A boy takes a picture of the Animorphs while they are demorphing in an alley. 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 battle that ensues, 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 that 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. Meanwhile, Marco is bored of just sitting around and decides to go over to the apartment of the boy who took their picture to try to steal his camera. He goes up the fire escape and enters through a window, but before he can even pick up the camera he gets bitten by a dog and flees home. Rachel falls down into Marco's stomach, and the Helmacrons as well as the rest of the Animorphs follow her, where they are shortly burnt by stomach acid before morphing sharks and following the Helmacrons into the bloodstream. In the bloodstream, Rachel notices a pathogen while looking at all of the different types of blood cells around them. They realise that when the Helmacrons reach the heart, they can stop it from beating with their weapons. Marco goes back to the apartment a second time, and while he is there someone comes home. He soon finds himself trapped in the closet and against Jake's orders, morphs a cockroach. The Helmacrons shoot at the cockroach's heart, after which everyone believes Marco to be dead until they remember that cockroaches can withstand severe trauma. In the meantime, the Animorphs get the weapons away from the Helmacrons by biting their legs. Marco is indeed alive, and they manage to get him to morph back to human. Holding the Helmacrons at gunpoint, they all return to the barn, and recharge the Helmacron's ship with the morphing cube. The Helmacrons leave earth again after promising to never come back. Later at home, Rachel researches on the computer and discovers that the pathogen she saw in Marco's bloodstream was rabies, and his near death experience actually saved him from the virus. Rachel considers calling him, but quickly dismisses it.Animorphs is an English language science fiction series of young adult books written by K. A. Applegate and published by Scholastic. It is told in first person, with all 6 main characters taking turns narrating the books through their own perspectives. Horror, war, dehumanization, sanity, morality, innocence, leadership, freedom, and growing up are the core motifs of the series.The story revolves around five humans, Jake, Marco, Cassie, Rachel, and Tobias, and one alien, Aximili-Esgarrouth-Isthill (nicknamed Ax), who obtain the ability to morph into any animal they touch. Naming themselves "Animorphs" (a portmanteau of "animal morphers") they use their ability to battle a secret alien infiltration of Earth by a race called the Yeerks. The Yeerks are a parasitic race of aliens resembling large slugs that take humans as a host by entering and merging with their brain through the ear canal. The Animorphs fight as a guerilla force against the Yeerks, led by Visser Three, and their program to take over the human race. Morphing into animals allows them to battle the various armies of aliens that the Yeerks use, but it also protects their identities. As far as the Yeerks know, only Andalites like Ax have the ability to morph, and if they knew that the Animorphs were mostly human they would be able to easily find out who they are. Protecting their identities becomes more and more difficult as the series goes on because though someone with the ability to morph can change into any animal that they touch, they can only stay in a morph for two hours or they will permanently become that animal. Throughout the series, we see how the war affects the characters in different ways, mentally and physically.