In this fifth book in the New York Times bestselling I Am Number Four series, the Garde are reeling from unbearable losses. Five has betrayed them. Eight is gone forever. Ella has been kidnapped.The others are scattered.

In Chicago, John makes the unlikeliest of allies: Adam, a Mogadorian who turned on his people. And he knows exactly where to hit them: their command base near Washington, D.C.During the assault, however, John and Adam learn it's too late. The Mogadorians have commenced with their ultimate invasion plans.

With a front-row seat to the impending invasion, Ella finds herself in the hands of the enemy. For some reason she's more valuable to them alive, and they'll stop at nothing to turn her.

Meanwhile, Six, Nine, and Marina make their way through the Florida Everglades, hot on the trail of the traitorous Five. With the development of a new Legacy, Marina finally has the power to fight back—if her thirst for revenge doesn't consume her first.

The Garde are broken and divided once again, but as long as one still stands, the battle for Earth's survival is not lost.