Crusading Dr. Lawrence Baxter uses radio broadcasts to warn the public against worthless cure-alls containing radium, specifically those produced by crooked drug manufacturer Kennedy. Larry's broadcast is canceled, however, and Larry believes that Kennedy is behind it. As he leaves the studio, he is approached by Jean Sterling, the daughter of famous medical researcher Professor Rexford Sterling, and she tells him that her father wants to sponsor him on a longer program. Larry meets with Sterling and agrees to the hour-long show, to be sponsored by Sterling's health magazine. When he returns to his office, Larry is approached by Pete Andorca, an old man who is ill from radium poisoning caused by Kennedy's rejuvenating tablets. Larry sends Pete to the hospital, while his friend, federal agent "Mac" McDonald, investigates. Larry begins his broadcasts for Sterling, who, without Larry's knowledge, is extorting money from the manufacturers Larry speaks against by telling them that if they buy advertising space in Sterling's magazine, he will stop Larry from mentioning them again. Larry discusses Pete's case on the air, even though he has not provided adequate protection for him, and Pete is tricked into leaving the hospital by Thompson, Kennedy's lawyer. Kennedy's men hide Pete in an isolated house, and after Larry discovers that Pete is missing, he finds out about Sterling's racket from Mac. Just before Larry confronts Sterling, Jean also finds out about the racket and tells her father to come clean or she will inform Larry, with whom she has fallen in love. Jean is shocked, however, when Larry arrives and tells Sterling that he wants in on the operation. Unknown to Jean, Larry plans to infiltrate Kennedy's syndicate and then expose it. That night Larry, Sterling and Jean go to Kennedy's health resort to meet members of a quack medical syndicate, and Larry obtains a list of the members, which he gives to Mac. Later, Larry tells Jean about his plan, and a relieved Jean agrees to leave town with her father to avoid harm. Larry is soon forced by Kennedy to begin work on a radium cold cure, and when Jean attempts to rescue him, she is also captured. The pair are tied together, but are freed by Kennedy's stooge, Andrews, who believes Larry's lie that he is suffering from radium poisoning. Kennedy kidnaps Sterling just as Larry and Jean escape, and they all rush to the house where Pete is being held. Mac arrives with the police just as Larry, Jean and Pete are about to be shot by Kennedy, and Kennedy is arrested. Later, Sterling resolves to go straight and tells Jean and Larry that he will send them a subscription to his new magazine as a wedding present.