Complex sentence: The next day Bruno concocts a plan with Shmuel to sneak into the camp to look for Shmuel's father, as they go about it, both children are rounded up along with a group of prisoners to be sent to the gas chamber.
Split into simpler sentences: The next day Bruno concocts a plan with Shmuel to sneak into the camp to look for Shmuel's father. As they search the camp, both children are rounded up along with a group of prisoners to be sent to the gas chamber.