The Silent Invasion

this term we are reading  a book called The Silent Invasion by James Bradley. This is a book that is set in Australia and is about a young boy named Callie who's sister has a infection which turns the people green and changes them. The officers of quarantine take people away from their family but we don't know why yet. Callie's dad has been taken and treated cruel and he doesn't want his sister  to suffer the same thing.

Callie plans to escape to the zone which is a place quarantine wouldn't go because they would die there so one night he escaped with Gracie and started heading to the zone

Questions
Did Gracie want to follow Callie?
What happens next?