Complex sentence: Harry Weston was prominently featured in a two-episode story arc in which Dorothy suffered from Chronic Fatigue Syndrome, and was instrumental in her proper diagnosis, being the only physician besides his referral who believed she was actually sick.
Split into simpler sentences: Harry Weston was prominently featured in a two-episode story arc in which Dorothy suffered from Chronic Fatigue Syndrome. He was instrumental in her proper diagnosis, being the only physician besides his referral who believed she was actually sick.