Dr. Hastie Lanyon was a close friend of both Dr. Henry Jekyll and Gabriel John Utterson. He was the first person to discover that Jekyll and his murderous "friend" Edward Hyde were one and the same person, a revelation that made Lanyon so spiritually ill that he eventually died of shock.
Dr. Jekyll and Mr. Hyde (1986)
Dr. Lanyon's role is much the same as in the novel, except he is aware of Jekyll's theories about separating the two selves, along with Utterson, and openly mocks them. He is also married and has a wife. After witnessing Mr. Hyde transform into Jekyll and learning the horrible truth, Lanyon becomes gravely ill and dies.