Complex sentence: When Pete, a coarse engineer who works on the boat, makes unwanted advances toward Julie, Steve engages him in a fistfight, whereupon Pete, who knows that Julie is part-black and Steve white, goes to the local sheriff and exposes the couple.
Split into simpler sentences: When Pete, a coarse engineer who works on the boat, makes unwanted advances toward Julie, Steve engages him in a fistfight. Pete knows that Julie is mixed and Steve white so he goes to the local sheriff and exposes the couple.