Complex sentence: The Wild Bunch are a gang of bandits who launder their loot of stolen gold via a fake goldmine, and the owner sends them after Beauregard because the latter's now-dead brother was in on the deal.
Split into simpler sentences: The Wild Bunch are a gang of bandits who launder their loot of stolen gold via a fake goldmine. The owner sends them after Beauregard because the latter's now-dead brother was in on the deal.