Complex sentence: Later, Amy and Ted Milner--a man she had an affair with before divorcing Mort--discuss her ex-husband's motives; she insists that Mort had become two people, one of them a character so vivid it became real.
Split into simpler sentences: Later, Amy and Ted Milner--a man she had an affair with before divorcing Mort--discuss her ex-husband's motives. She insists that Mort had become two people, one of them a character so vivid it became real.