Simplify the following text for a Grade 4 native English-speaking person.
Original: Akima , Cale and others from Korso 's ship work together to defend the Titan against the Drej attack . Cale thinks that the energy that makes up the Drej and their ships may be used to power up the Titans systems .
Simplified: The group is then attacked by the Drej , and Cale and Akima are captured .