In New York City, interior decorator Jan Morrow shares a party phone line with songwriter Brad Allen, who continually ties up the line singing the same love song, “Inspiration,” to his many girl friends. When Jan’s complaints yield only disdain from Brad, she reports to the phone company that Brad is a sex maniac, prompting the manager to launch an investigation. The researcher, however, is a single female who is so immediately entranced by the handsome womanizer that she waives the complaint. Meanwhile, Jan refuses a gift of a convertible automobile from her wealthy client and would-be suitor, Jonathan Forbes. The next morning, Brad calls Jan and insinuates that it is her inactive sex life that causes her to hound him, after which she icily suggests a time-share arrangement under which they each use the phone for half of every hour. Alma, Jan’s drunkard maid, has been listening in, and now confirms Brad’s view that Jan needs a more active sex life. Jan, however, considers all her paramours lacking, including Jonathan. When he later proposes, she explains that he fails to make her “hit the moon” with passion. A frustrated Jonathan grumbles about Jan to Brad, who is an old friend and the writer whom Jonathan has hired to write a musical play. When Brad, who has never seen his party-line partner, recognizes her name, he is fascinated by Jonathan’s description of her many assets. Although he scoffs at Jonathan’s advice to curtail his playboy lifestyle in favor of marriage, Brad later calls Jan to apologize for his earlier behavior, growing even more intrigued when she remains impervious to his charms. That night, Jan attends a party hosted by her rich client, Mrs. Walters, whose college-age son Tony offers to drive Jan home. Once on the road, Tony attacks Jan with youthful fervor, forcing her to agree to accompany him to a club, where, unknown to her, she sits next to Brad and his date, Maria. After overhearing Jan’s name, Brad notes her lovely figure and schemes to seduce her, and knowing that she would never speak to him, devises a new identity: Rex Stetson, chivalrous Texas rancher. “Rex” soon enchants Jan, who is instantly attracted to the tall, apparently guileless country man. While she muses on his trustworthy appeal, he silently deduces that it will take him only five dates to sleep with her. Later that night, Brad hatches a plan to further endear Rex to Jan by calling and pretending to be first Rex and then Brad, interrupting to warn Jan that he has heard Rex on the line and considers him a rake. Jan sneers at Brad’s assumption but the next night, when Rex brings her to his hotel room, she is on guard. He merely retrieves his coat, however, causing her to beg his forgiveness for her untoward suspicions. They then take a hansom cab though the park, during which Brad’s handling of the horses delights Jan but horrifies the driver. At dinner, Brad spots Jonathan near the entrance and deters him from coming over to their table by tricking him into thinking he has an unattractive date. Brad and Jan spend the next few days together, enjoying each other so much that she agrees to break a date with Jonathan for him. Jonathan guesses correctly that Jan is in love with someone else, and although he wishes her luck, he hires a private investigator to look into his competition. Later, Brad avoids running into Jan in Jonathan’s hallway by stepping into an obstetrician’s office, where he startles Nurse Resnick and Dr. Maxwell by asking for an examination. Soon after, Jonathan’s investigator provides photos of “Rex” that compel Jonathan to confront Brad. He tails Brad and Jan to a club, where he clandestinely warns Brad to leave Jan and spend the next weeks secluded in Jonathan’s Connecticut home. Brad appears to be remorseful and conpliant but secretly asks Jan to accompany him to the country, where the couple enjoys a romantic rendezvous by the fire. Jan is eager to make love with Rex, but at one point discovers some sheet music and, upon playing it, recognizes the song as “Inspiration.” Realizing his ruse has been uncovered, Brad tries to proclaim his love to Jan, but just then Jonathan arrives and Jan flees with him to the city. Despite Jonathan’s desire to woo Jan, her constant sobbing on the ride home unnerves him. They stop at a diner, and after he slaps her to help her gain her composure, the appalled patrons assume he is a cad and knock him out. Three days later, a distraught Brad begs Jonathan to help him win back Jan, but when she visits Jonathan’s office and spots Brad, she dashes away. He follows her into the ladies’ room, managing once again to arouse the interest of Dr. Maxwell, who hopes Brad may prove to be the world's first pregnant man. Desperate, Brad turns to Alma, who calls herself “a devoted listener” to his phone calls and accepts his offer to go to a bar and discuss his situation with Jan. The next morning, a brutally hungover Brad recalls Alma’s advice to hire Jan to decorate his apartment, and schemes with Jan’s boss to manipulate her into accepting the job. Jan spends the next few days converting the apartment into a nauseating bachelor pad, complete with animal prints, hanging beads and a harem decor. When Brad sees it, he is infuriated and storms into Jan’s apartment, dragging her from her bed in her pajamas and carrying her to his apartment. Brad's brash behavior inspires Jan’s elevator operator to flirt with Alma. At Brad’s apartment, he launches into an angry tirade, of which Jan registers only that he wants to marry her. When he tries to stomp out, she flicks one of the switches she has installed, which locks the door from the inside. Finally understanding that she loves him, Brad sweeps Jan into his arms. Three months later, Brad returns to Jonathan’s building to announce Jan’s pregnancy, but is stopped by Nurse Resnick and Dr. Maxwell, who by intrigued at the scientific implications of Brad’s declaration that he is having a baby.