In the beginning the Giver teaches Jonas about "Sameness", in the book sameness means that no one ever makes there own choices. Jonas doesn't like the thought of sameness. He wants to be able to make his own decisions for his own life.
Jonas wants to change his community back to how it was before. He wants them to have the memories too, good and bad. He wants a normal community where everyone makes there own decisions and picks there own assignments, family units, and spouse.
Jonas and the Giver decide to make a plan so that they can have a normal community with no sameness. They decide to make a big plan and for Jonas to break a big rule.
Jonas finds out that Gabe is going to be released and the whole plan changes. Instead of leaving the community in two weeks he decides to leave that night. Jonas takes Gabe with him and they decide to leave there little utopia and head elsewhere.