Complex sentence: When she returned, Gordon had long since divorced his wife Barbara, and the two began a serious and open relationship, eventually resulting in Gordon proposing to her on a night when the police station was under attack a trio of electric-based super-villains.
Split into simpler sentences: When she returned Gordon had long since divorced his wife Barbara, and the two began a serious and open relationship. Gordon finally proposed to Sarah on the night that the Police station was under attack a trio of electric-based super-villains.