A woman running a trucking company falls for the reporter out to expose her business practices.

Margaret J. Drew, known as "M. J." by her intimidated employees, has taken over command of the vast Drew financial empire from her late father. When reporter Michael Holmes begins to publish exposes about Drew's tyrannical employment practices, the imperious M. J. demands that he be investigated. Mike, who has gleaned his information from his friend, Drew driver Johnny Johnson, is driving with Johnny one day when they see a woman whose car has broken down along the road. When Johnny pulls over to help the woman, she identifies herself as a Drew spotter and cites him for carrying a passenger and stopping his vehicle. Furious about M. J.'s unjust policies, Mike decides to crash the wedding of her younger sister Vivian. At the Drew estate, meanwhile, Vivian's protests that she is in love with filling station attendant Joe Krim are met with a cold heart and deaf ears by M. J., who insists that she proceed with her marriage to Stephen Pettingill, the scion of a steel family. When M. J. steps outside and sees Mike, her knees buckle, an affliction that strikes the female members of the Drew family whenever they are confronted by a man to whom they are attracted. Dismissing her wobbly knees as a "liver ailment," M. J. mistakes Mike for a bodyguard hired to patrol the ceremony. After drinking too much brandy during the wedding, Mike becomes inebriated and amorous, and when he eagerly kisses Vivian, M. J. thinks that he must be Joe and decides to expose him as a fortune hunter. Summoning Mike to her room, M. J. hands him $1,000 in marked bills. Failing to recognize his nemesis, Mike kisses M. J., who then orders his arrest for blackmail. Upon discovering their error, M. J.'s attorney Marsh arranges Mike's release and warns her that the reporter could sue for false arrest. When Mike appears at her office to discuss the terms of an agreement, M. J.'s knees buckle and she excuses herself to visit the doctor. Becoming impatient, Mike gives his Brooklyn address to Marsh and instructs him to tell M. J. to meet him there that night. The doctor, meanwhile, prescribes sedatives to combat M.J.'s weak knees. That evening, M. J. goes to the Brooklyn address and is greeted by Johnny, Mike's neighbor, who has never met the head of Drew Enterprises and consequently mistakes M. J. for Mike's sweetheart. Before meeting Mike, M. J. swallows two pills, and soon after passes out. The next morning, M. J. is alarmed when she awakens in Mike's bed wearing his pajamas, but Mike assures her that Susie, Johnny's wife, put her to bed. Johnny then enters the room and provides Mike with more details about the company's injustices. Later that morning, M. J. surprises her employees when she strides into the office wearing the previous night's evening clothes. Vivian, who has returned early from her honeymoon, is waiting at the office to tell her sister that Steve was called back on business. As M. J. changes into her work clothes, Mike enters, addresses her as "Maggie," and offers to sign a release promising not to sue if she will have dinner with him. M. J. agrees, but after Mike signs the document, she conveniently remembers that she is busy, but then discovers that Mike has signed the release as "Benedict Arnold." That night, in a drenching rain storm, M. J. ventures to Brooklyn to keep her bargain with Mike, and Johnny tells her that Mike is at the Drew employees' dance and offers to drive her there. Along the way, Johnny is cited by one of the Drew company spies for carrying a passenger. At the dance, M. J. finds Mike and asks to keep her dinner date with him. When the dance contest is announced, however, Johnny grabs M. J. as his partner and begins wildly jitterbugging with her. Crane, the head of Drew personnel, is shocked to see his boss on the dance floor and awards her first prize. After the dance, Mike, M. J., Susie and Johnny return to the apartment and get drunk. When Johnny insists upon driving the inebriated M. J. home, they all pile into the truck, and Mike climbs into the driver's seat and kisses M. J. After pulling into the Drew driveway, Mike escorts M. J. into her house while the watchman informs the astonished Johnny that his friend Maggie is really M. J. Drew. When M. J. tries to seduce Mike, he resists and then passes out. At the office the next morning, M. J. learns from Crane that Johnny and eleven other drivers have been fired for taking their trucks to the dance, and Crane listens in disbelief when M. J. orders them rehired and granted a five dollar raise. Back at the house, meanwhile, Mike awakens wearing the cook's nightgown and is relieved to discover that the butler put him to bed. Soon after, Johnny barges into the bedroom and blames Mike for the drivers' firing. Mrs. Drew, M. J.'s addle-brained mother, then enters and asks Mike to lend Steve $30,000 so that he can reopen his family's steel mill and bid on a defense contract. After extracting a promise from Steve that he will hire all the drivers, Mike agrees to the loan and proceeds to M. J.'s office, where he offers to sign the release in exchange for $30,000. Feeling betrayed, M. J. accepts his terms and then attends a business meeting. Unable to keep her mind on her speech, M. J. finds her thoughts interrupted by images of blissful domesticity and after adjourning the meeting, she hurries to see the doctor, who diagnoses her as being lovesick. Returning home to chair a stockholders' meeting, M. J. is confronted by her mother, who tells her that Mike gave Steve the $30,000 to hire the drivers. Finally realizing that she is in love with Mike, M. J. hurries to Brooklyn but Johnny and the other drivers refuse to let her see him. Susie then arrives and tells M. J. that Mike is waiting for Johnny to pick him up. Soon after, Johnny meets Mike and instructs him to climb in the back of the truck and close the door. When one of the Drew spies spots the truck, M. J. opens the doors and tells Johnny to drive to the nearest minister.