 She has returned to Earth, overseeing a Yeerk bio-weapons program to allow them to venture into deep waters; this is a requirement made by the Yeerk command for the invasion of Leera, a planet covered almost entirely by oceans.The research is conducted in the waters around Royan Island.The Animorphs infiltrate the facility, and discover that the Yeerks are trying to create super-intelligent sharks which can be infested and controlled, because in their natural state, the sharks' brains are not big enough.