A German scientist develops a stain for diagnosing tuberculosis, an effective serum to cure diphtheria, and a chemical for attacking syphilis.
In a clinic Dr. Hans Wolfert (Sig Ruman) complains that Dr. Paul Ehrlich (Edward G. Robinson) does not follow rules. Ehrlich tells his wife Hedvig (Ruth Gordon) he wants to quit, but his daughters need milk. In a laboratory Ehrlich shows Dr. Emil von Behring (Otto Kruger) his dyes. Ehrlich is warned he may be fired if he does not conform, but he leaves work to tell Dr. Robert Koch (Albert Bassermann) that a dye could make the tubercle bacillus he discovered visible. Ehrlich loses his job and experiments, coughing. Hedvig heats his room, making a stain work. Behring has Ehrlich test himself for tuberculosis. Ehrlich shows Koch the stain and is given a position, because doctors can now diagnose tuberculosis. Ehrlich goes to Egypt for a cure and treats snakebite, learning the father became immune from previous bites. Ehrlich returns to Koch and works on snake venom. Behring says his diphtheria serum failed and gets angry. Ehrlich explains how antibodies can be increased by injections in animals. A diphtheria epidemic ravages German children. Koch lets Ehrlich and Behring give the sermon to half, but they inject all forty children. They fear the end of their careers, but minister Althoff (Donald Crisp) tells Ehrlich that all forty survived and asks him to work on a typhoid serum.
Ehrlich develops his side-chain theory over fifteen years. A committee learns of his research with mice, rabbits, and guinea pigs. Wolfert reprimands him for hiring an Oriental as "unGerman." Reading that syphilis spirochetes were discovered, Ehrlich searches for "magic bullets," chemicals to kill microbes. Behring visits Ehrlich and says that Althoff wants him to give up using chemicals for cures. Behring and Ehrlich disagree, and Ehrlich's funds are cut by 50%. Hedvig goes to rich Franziska Speyer (Maria Ouspenskaya), who invites Ehrlich to dinner. He explains his work on syphilis and persuades her that tests are worthwhile. After 606 tests, a monkey recovers. Ehrlich tells his staff human experiment must be secret. Dr. Morgenroth (Edward Norris) suspects that Ehrlich will inject himself and beats him to it. Dr. Lentz (Henry O'Neill) asks patients to volunteer, and a blind man gradually regains his vision. Ehrlich declines to release his specific until he checks for complications; but doctors persuade him to help those in need.
Orders come in, and Ehrlich collapses. Dr. Lentz calls him that a patient died. Wolfert reports deaths by 606 to a newspaper. Althoff urges Ehrlich to sue for libel. In the trial Ehrlich admits arsenic does kill some; but symptoms can lead to stopping treatment to prevent death. Behring testifies that 38 deaths were caused by 606, but he says 606 cures syphilis. Ehrlich is vindicated, and Wolfert is sentenced to one year. Before he dies, Ehrlich says diseases of the soul, such as greed, hate, and ignorance, must also be cured.
This inspiring true story of important medical advances
is particularly timely as Wolfert opposes Ehrlich because he is
a Jew. Yet his discoveries saved thousands of Germans as well
as others. Ehrlich developed practical theories for treating disease
and pioneered chemotherapy.