In Budapest in 1935, Dr. Paul Venner, a medical researcher, is stunned when a published article attributes the conclusions of his research on the biochemical origins of schizophrenia to Professor Hermann von Reiter, his supervisor. Although von Reiter apologizes to Venner and claims that a correction will be sent to the scientific journal that published the article, he instead arranges for Venner to be exiled from Hungary without his research materials. Later, in London, Venner is faced with the task of starting again from scratch when he encounters his old teacher, Dr. Drewett, a psychiatrist at a private sanitarium in Scotland, who arranges for Venner to continue his work at the sanitarium. Venner, a blunt man absorbed in his research, is disappointed to learn that his assistant is Dr. Mary Murray, a young woman with few qualifications. At first, Venner's harsh criticisms upset Mary, who would like to experiment with Venner's drugs in China, where she intends to work as a medical missionary. After Drewett tells Mary that Venner had a mentally ill parent, however, her sympathy for him helps her to better understand his demands. Although she is warned by Miss Leeming, the sanitarium secretary, that Venner is a hurtful person, Mary develops a successful working relationship with him. Venner's drugs help many of his patients, but one of them, Foster, is resistant. Venner realizes that without an examination of the brain tissue of someone that he has treated, he will not know for sure if the drugs are effective. Then, when they are on the verge of success, Mary tells Venner that she plans to leave soon for China. Stunned, Venner begs her to stay and asks her to marry him. Mary admits that she loves him deeply and the next day they buy an engagement ring. When Foster dies, Venner does an immediate postmortem, without waiting for the permission of Foster's wife. Although the autopsy proves the efficacy of Venner's drugs, it is illegal, but Drewett reminds the sanitarium of its value to medical science and convinces the other doctors not to report it to the coroner. Leeming, who is romantically obsessed with Venner, threatens to ask Mrs. Foster to prosecute Venner if he marries Mary. When Venner responds that he has the evidence necessary to defend himself, Leeming sets the lab on fire to destroy it. Mary sees the flames and saves Venner's research by throwing it out the window, but dies in the fire. After Venner's paper is published, he is deluged with offers, but he now intends to travel to China to carry out Mary's work.