"You know our stories are true. You know why we fight. You must discover their secrets. You must learn from our mistakes. They are hiding, just like us. They plan to destroy your planet. They destroyed ours. We cannot let this happen again."

It has been over a year since the invasion of Earth was thwarted in Pittacus Lore's United as One. But in order to win, our alien allies known as the Garde unleashed their Loric energy that spread throughout the globe. Now human teenagers have begun to develop incredible powers of their own, known as Legacies. To help these incredible and potentially dangerous individuals - and put the world at ease - the Garde have created an academy where they can train this new generation to control their powers.

In Beatrice Prior's dystopian Chicago, society is divided into five factions, each dedicated to the cultivation of a particular virtue - Candor (the honest), Abnegation (the selfless), Dauntless (the brave), Amity (the peaceful), and Erudite (the intelligent). On an appointed day of every year, all sixteen-year-olds must select the faction to which they will devote the rest of their lives. For Beatrice, the decision is between staying with her family and being who she really is - she can't have both. So she makes a choice that surprises everyone, including herself.

The Republic of San Magnolia has long been under attack from the neighboring Giadian Empire's army of unmanned drones known as the Legion. After years of painstaking research, the Republic finally developed autonomous drones of their own, turning the one-sided struggle into a war without casualties—or at least, that's what the government claims. In truth, there is no such thing as a bloodless war.

Syd Chambers grew up on Earth with his human mother and barely remembers his alien father from Denza, who left on a mission when Syd was very young. After leaving Earth, Syd learned the truth of his father’s disappearance on the planet Ashfall—his father had died protecting a devastating secret about the history between humans and Denzans.