Sage, a teenage boy living somewhere in Asia, grieves Aiden, his best friend, who died after being hit by a car while the two were biking together. Aiden's mother, a technology businesswoman, created AIDEN, an artificial intelligence program directly implanted into people's brains, that has the voice and the passion for exploration of her dead son. Sage receives the software and uses it to grieve as he begins to lose the distinction between the AIDEN program and his friend.

Aiden's father, Levi, develops a friendship with Sage but is suspicious of the software as protests against it sweep the nation. Aiden's mother's software has the potential to be implanted into the brains of children across the country. Levi gives Sage letters that Aiden wrote for him; they are musings on the possibility of an alien invasion and what the two boys should do to prepare. Sage develops a fascination with disaster preparedness and becomes defensive whenever the AIDEN software is criticized. The program begins to bleed into the nation's entertainment and gaming software as Sage goes into college.