Complex sentence: He had given his best friend Mark a sandwich laced with a hallucinogenic drug for a joke, when Mark, still high, falls to his death from a window, Edward is racked with guilt afterwards and gives up on life.
Split into simpler sentences: He had given his best friend Mark a sandwich laced with a hallucinogenic drug for a joke. After Mark, still high, falls to his death from a window, Edward is wracked with guilt afterwards and gives up on life.