Complex sentence: The episode marked the first major developments in the Watson case, a major season one story arc based on the real-life slaying of Latonya Kim Wallace is featured in David Simon's non-fiction book', from which the series was adapted.
Split into simpler sentences: The episode marked the first major developments in the Watson case, a major season one story arc based on the real-life slaying of Latonya Kim Wallace. The Wallace case was featured in David Simon's non-fiction book', from which the series was adapted.