The Sacrifice is the 52nd book in the Animorphs series, written by K. A. Applegate. It is known to have been ghostwritten by Kim Morris. It is the final book to be (fully) narrated by Ax. Plot summary 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 masse. 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 the 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 announces that she and her parents will not be going on the mission, since they cannot face risking so many Controllers' lives. She gets into an argument with Rachel over it, and then another with Jake. With Rachel, Cassie is accused of essentially giving up in the fight against the Yeerks, which makes Cassie admonish Rachel for how horrible her attitude has become, even to the point where even Rachel's own mother cannot stand to be in her presence. With Jake, who initially tries to defuse Cassie and Rachel's dispute, Cassie derides him for being so willing to risk human lives, adding that she had previously thought that she had known him better than that. However, Jake fires back that Cassie had acted as though she had thought that she had known what was best for him and everybody on the team, subtly referring to her actions with Tom two books prior. As a result, the stress of the arguments causes Cassie