The Sacrifice
K. A. Applegate
 During a reconnaissance flight taken by Rachel, Ax, and James, the Animorphs learn that the Yeerks are herding people into the subway system. The subways have been redirected to the Yeerk pool complex, where humans are being infested en mass. Back at the Hork-Bajir valley, Rachel makes her report to Jake. Marco comes up with a plan to use the subway system to destroy the Yeerk pool by loading one of the pool-bound trains with explosives and detonating once the train reaches its destination. Despite some resistance from Cassie, the Animorphs agree to carry out the plan. Later that night, Ax sneaks away from the camp with the zero-space transmitter constructed by Marco's father. Ax contacts the Andalite military and tells them of the Animorphs' plan to destroy the Yeerk pool. The Andalites do not support the plan and feel that the war for Earth is lost. Ax is ordered to sabotage to Animorphs' operation to destroy the Yeerk pool so that the Yeerks will continue concentrating the majority of their forces on Earth, allowing the Andalites to wipe them out more easily. The next morning, the Animorphs finalize their plan to destroy the Yeerk pool. During the meeting, Cassie breaks down and confesses that it was she who allowed Tom to escape with the morphing cube. Despite this realization, the other Animorphs forgive Cassie for her actions and continue planning the operation, with the exception of Ax, who feels a cold hatred towards Cassie for letting Tom take the cube. After the meeting, Ax pulls Cassie aside and asks her to justify her actions. She recalls Aftran 942 and the Yeerk Peace Movement, and speculates that the morphing technology could give the Yeerks a means to abandon their policy of infesting sentient beings and instead morph new bodies. Ax concedes that he encountered a Yeerk who planned to do this on the subway mission, though he also speculates that the Yeerk could have been lying. After speaking with Cassie, Ax talks with Tobias, who voices his support of Cassie's reasoning. Ax decides to disobey his orders and not sabotage the plan to destroy the Yeerk pool. The next night, Ax leads the other Animorphs' parents through the woods towards a National Guard base where the Animorphs hope to steal the explosives they need for their operation. Upon reaching the base's perimeter, the parents pose as lost campers in need of medical attention. The National Guardsmen load them into a truck and drive towards the base, with Marco clinging to the back of the truck in gorilla-morph. The other Animorphs follow as either fleas on Marco or in various bird-of-prey-morphs. Upon reaching the National Guard base, the Animorphs begin searching the various warehouses for the explosives. Once they are found, they begin loading the explosives onto the trucks commandeered by Rachel's mother, Naomi, and Cassie's father, Walter. On their way out, the Guardsmen, alerted by an alarm, halt the trucks. Rachel initially tries to run them down, but is stopped by Ax. Jake and Naomi speak with the Guardsmen's commander, Captain Olston, and explain the situation. The Guardsmen agree to assist the Animorphs in their operation. The Animorphs' parents drive the trucks into the city, where the Animorphs themselves, along with several National Guard troops disable the Yeerk forces guarding the subway station. The Animorphs are forced to fight with several morph-capable Controllers, with several using wolf-morphs (the same battle morph as Cassie). The Guardsmen kill several of the wolves, making Ax fear that Cassie has been killed in a friendly fire incident. Fortunately, Cassie survives the battle and Ax silently reconciles with her. Marco, Ax, and Cassie volunteer to accompany the train to the Yeerk pool, now loaded with explosives. Ax keys the detonator so that the explosives will go off five minutes after reaching the Yeerk pool, giving the Controllers and hosts there time to escape. The subway train jackknifes into the Yeerk pool. Ax, Cassie, and Marco survive due to being in various insect-morphs during the collision. They demorph and warn those in the pool of the situation, and then begin freeing caged-hosts. Visser One briefly emerges to do battle, but leaves after Marco tells him of the impending explosion. Ax, Cassie, and Marco leave the doomed Yeerk pool complex just as the bombs detonate. The Animorphs survey the devastation. The destruction of the Yeerk pool destroys a large area of the Animorphs' home town. Jake privately thanks Ax for his participation, and Ax silently pledges his continued support to his prince. * The Yeerks abandon their infiltration strategy for conquering Earth. * The Yeerk Pool is destroyed.