What role does Dr Lanyon play?

Dr. Lanyon is a key character in Robert Louis Stevenson's "Strange Case of Dr Jekyll and Mr Hyde." He is a reputable physician and a close friend of Dr. Jekyll, representing the rational and scientific perspective in contrast to Jekyll's increasingly unorthodox experiments. Lanyon becomes a crucial figure in the story when he witnesses the transformation of Jekyll into Hyde, leading to his shock and eventual demise. His character underscores the themes of duality and the conflict between science and morality.