Maximum Ride and the other members of the Flock have barely recovered from their last arctic adventure when they are confronted by the most frightening catastrophe yet. Millions of fish are dying off the coast of Hawaii and someone – or something – is destroying hundreds of ships. Unable to discover the cause, the government enlists the Flock to help them get to the bottom of the disaster before it's too late.

While Max and her team are exploring the depths of the ocean, their every move is being carefully tracked by Mr. Chu – a criminal mastermind with his own plans for the Flock. Can they protect themselves from Mr. Chu's army of mercenaries and save the ocean from utter destruction?