Complex sentence: They head to the junkyard, where Scamp retrieves his collar and traps Buster under piles of junk, before the gang members abandons him, and they can go to find families.
Split into simpler sentences: They head to the junkyard, where Scamp retrieves his collar. Scamp then traps Buster under piles of junk, but the gang members do not help and instead abandon him, so they can go to find families.