Dr. Arthur Kemp was the friend of Dr. Jack Griffin who served as an assistant to Dr. Cranley. Unlike Griffin, Dr. Kemp was a thoroughly incompetent scientist as well was an opportunistic coward. He continually criticized Griffin for his experiments with monocane, and secretly coveted Griffin's fiancee (and Dr. Cranley's daughter), Flora.
When Griffin disappeared and went to the remote village of Iping, Kemp attempted reported his colleague's questionable experiments to Dr. Cranley and tried to woo Flora: Although he managed to convince Cranley that Griffin was up to no good, he failed to persuade Flora to forget about her beloved Jack. Shortly after this, Griffin, now made invisible as a result of his monocane experiments and hunted as a criminal by the police in Iping, turned up in Kemp's house seeking his old colleague's assistance.
Although Kemp initially went along with Griffin's plans, helping him retrieve his notebooks from the Lion's Head Inn (where, unknown to Kemp, Griffin murderered Inspector Bird), Kemp soon grew too afraid of Griffin to continue assisting him. Not only did he alert both Flora and Dr. Cranley to Griffin's whereabouts, but the police as well. Kemp was marked for death by a furious Griffin, and despite intensive police protection and a daring plan by Inspector Lane to get Kemp safely out into the country disguised as a police officer, Griffin managed to make good on his threats: He tied Kemp up, put him into his car, and then sent the car over a cliff. Kemp perished in the crash.