Complex sentence: He tells her he prefers her to go ahead and leave so she will not have to face the brutal ugliness that will befall him during the trial, but he lets her know he will welcome her return when the ordeal is over.
Split into simpler sentences: He tells her he prefers her to go ahead and leave so she will not have to face the brutal ugliness that will befall him during the trial. But he lets her know he will welcome her return when the ordeal is over.