So they're convinced that their plan is going to work.
Their plan definitely does not work.
We cut to the image of Jonas, who has been "forced to flee" that very night, two weeks before the Ceremony, guiding his bicycle over the bridge in the darkness.
What happened? Now we go back in time to find out.
So Jonas is eating dinner with his family when his Father cheerily announces that Gabriel is going to be released the next morning. They just haven't been able to get him to sleep through the night when they brought him to the Nursery, so it's bye-bye for this little toddler.
Now we cut back to Jonas, still crossing the bridge on his bike in the dark.
Actually, it's not his bike; it's his Father's. He took his Father's bike because it had a baby seat attached to the back.
Which means, of course, he took Gabriel, too.
Before he stole the toddler, Jonas transmitted to Gabriel the memory of a rocking hammock. Fortunately, this kept the little tyke asleep and quiet while Jonas got them out of the house.
As time passes, Jonas tires as he continues to pedal and pedal. When dawn breaks, he stops, puts the bike down, and has breakfast with Gabriel by the side of a stream.
He hides them in the grass and they both sleep through the daylight hours.
Days go by, and Jonas is still biking. He's gotten into a routine now of hiding in the day and traveling at night. Mostly, he worries when the low-flying search planes come by overhead, especially because he knows they have heat-seeking devices. (No, really, the text says "heat-seeking devices." Apparently Jonas learned about it in school.)
When he sees the planes, Jonas tries to hold on to memories of cold, in the hopes that that will neutralize the heat-seekers.
Jonas notices that his memories are fading a bit, which is what he and The Giver had expected: as he moves further and further away from the community, the memories should be released to the citizens and thus fade from his mind.
As the days go on, the planes become less and less frequent. Finally, they stop altogether.