K. a Applegate

"When Tobias and his friends were given the power to morph, they were also given an important warning: Never stay in a morph for more than two hours. But Tobias broke the time limit, and now he's trapped in the body of a hawk -- forever. When he discovers an important Yeerk secret, Tobias knows he has to do everything in his power to destroy it. But to do so, he'll have to contend with a part of himself that's wrestling for dominion. A part that isn't...

"It begins with the dreams. Cassie has been having strange nightmares of a voice calling to her from deep beneath the ocean. They're unsettling, but it isn't until Cassie discovers Tobias has been having dreams too--the exact same dreams, of a voice pleading for help--that she decides it's time to start listening. When pieces of debris wash up on shore, marked with alien writing, the team realizes they may still have allies in the fight for Earth--allies...