Based on a novel by Lloyd C. Douglas, a surgeon sacrifices his career to protect his mentor and then risks his life in research.
Dr. Newall Page (Errol Flynn) kisses adoring nurse Frances Ogilvie (Margaret Lindsay) and warns her. Page learns that Dr. Endicott postponed Mrs. Dexter's surgery. Mrs. Dexter (Spring Byington) listens by radio to a sermon on the red and green lights by Dean Harcourt (Cedric Hardwicke). Page admires Mrs. Dexter's faith. By the sea Page meets Harcourt, who walks with two canes. Endicott is late, and Page operates on Mrs. Dexter. Dr. Endicott (Henry O'Neill) returns and takes a call about his falling stocks. Endicott takes over surgery, and Mrs. Dexter dies. Endicott is blamed for cutting the artery too close. Page refuses to testify, and Endicott blames no one. The board advises Page to resign. Page drinks and tells Dr. John Stafford (Walter Abel) he is grateful that Endicott taught him. John says good-bye and goes to Montana to work on spotted fever. John asks Ogilvie to tell the truth, and she is urged to go to Harcourt, who says Page had his reasons. Harcourt asks Ogilvie to question the next person, who is Phyllis Dexter (Anita Louise). Harcourt asks Ogilvie to pray. Phyllis cries and blames Page, but Harcourt asks her to pray about hatred's effects.
Page calls on Ogilvie and finds Phyllis there. Ogilvie tells Phyllis that Page is Walker. Page goes to Harcourt to argue with him. Harcourt says he won a victory over Endicott, who will be left behind. Harcourt, though crippled, waits for the green light. Page advises Harcourt to rest. Phyllis comes in and goes out with "Walker." Harcourt invites them and Ogilvie to dinner. Phyllis realizes who Page is and walks off. At Harcourt's Phyllis asks Ogilvie why she lied. Ogilvie says that Page is good. Phyllis and Ogilvie go to see Page; but he went away to help John fight spotted fever. John shows Page the valley of death. Page visits a sick man. John writes to Ogilvie that Page needs rest. Page gives himself a shot of half-virulent spotted fever. He survives but then puts a tick on himself. Phyllis goes to Page, and they embrace. He tells her to go but collapses. John tells Phyllis of Page's experiment. Ogilvie calls on Endicott and tells him Page has spotted fever. Page tells John his symptoms. Endicott and Ogilvie fly to Montana. Page's fever goes up to 104. Endicott says he must live. Page survives, and they make a vaccine. Ogilvie stays to help John. Page and Phyllis attend Harcourt's sermon.
Deep faith in spiritual justice underlies this drama of a sacrificing doctor, who, as Ogilvie says, needs no religion because he is already good. Endicott learns a hard lesson. Phyllis learns to forgive, understand, and love. Ogilvie, like Page and John, has a true calling but also needs love.