An inventor tests his new carburetor and hopes to win over the woman who seems to like an engineer.
Jane (Wendy Barrie) has been hired to do publicity and meets engineer Frank Lawson (Weldon Heyburn) and auto tester Terry Martin (James Stewart) after he overturns a car. Terry shows Jane the modern auto factory, and Frank takes her into the lab, where Terry and Gadget (Ted Healy) are not allowed to go. Gadget flirts with receptionist Fanny Lane (Patricia Wilder). Terry is working on a new carburetor. Gadget tampers with Frank's car so that Jane can go with Terry; but she declines to attend a party with him. Frank tells Jo Sanderson (Una Merkel) he hopes to see her at the party, so he can go with Jane, who says she is busy. At the party Terry sees Jane arrive with Frank. Terry sits with Gadget and Fanny. Jane sees Terry drinking and tries to explain why she came with Frank. Jo talks with Terry while Jane dances with Vice President Dean (Ralph Morgan).
Dean tells Terry to let Frank work on the carburetor with him. Jane tells Terry that his invention will be tested at the Indianapolis 500. Frank suggests a horizontal inlet valve. A driver is killed, but Terry and Gadget qualify. Jane goes back with Dean. She joins Terry for lunch and explains that she does not prefer Frank. Jane and Jo agree that Terry has an inferiority complex. Terry doubts the car, but Frank assures Dean it is all right. Terry leads but goes into a skid. Gadget is badly hurt, and Terry is in the hospital too.
Jane visits Terry, who resents Frank. Jane says she persuaded Dean to let Frank help Terry. Recovering Gadget urges Terry to go back to work; but Dean denies Terry a speed test. After Jane talks on the phone in Dean's office, Terry gets permission; but Terry refuses to work with Frank. Gadget is in a wheelchair, and Fanny asks him to forgive her. They all go to a barn dance, and Terry tells Jane he hopes to win her with the money from the speed record. On a dry lake Terry accelerates the Falcon car; but a fire starts. George pulls Terry out of the car and then drives him back to the hospital. Dean tells them that Jane is the niece of the company president. Frank offers to drive Jo back to Los Angeles, and Jane tells Terry to stop being a sap.
This romantic drama portrays two women in strong positions with a modern company while a mechanical inventor from a poor family has to overcome his own doubts.