A cynical songwriter upsets the lives of three musical sisters.

In Connecticut, widowed music professor Gregory Tuttle has three daughters, who share his love of chamber music. Fran, his oldest, becomes engaged after only seven dates to the chubby but successful Robert Neary. Amy, who is ambivalent about her admirer, the soft-spoken Ernest Nichols, is not expecting to marry soon. The youngest daughter Laurie has no suitor and muses that the trouble with most marriages is that there are "not enough laughs." She jokingly offers Amy a "double or nothing" proposal, in which they either have a double wedding or remain spinsters together. Later, Alex Burke, a confident New York composer and dog lover, introduces himself to Gregory as the son of an old friend, and finagles an invitation to room at the Tuttle house while he composes a musical he has been commissioned to write for Broadway. Alex's take-charge personality charms all three Tuttle sisters, but he falls in love with Laurie, and gives her a bracelet during an outing at the beach. Soon after, Barney Sloan, a music arranger, comes to town to work with Alex on the musical and despite Barney's sullen manners, Laurie and Aunt Jessie, Gregory's spinster sister, warm up to him. After listening to Barney enumerate his misfortunes and complain that fate is against him, Laurie feels challenged to help him improve his attitude. She also recognizes his great, untapped talent and urges him to complete a song he has partially written. Although he hides his true feelings behind cynical jests, Barney is touched by her efforts. Later, when Alex proposes to Laurie, she accepts by saying "it might be fun" and they announce their engagement at Gregory's birthday party. Surprised by the news, Fran decides to move up the date of her own wedding. Amy, who is secretly infatuated with Alex, becomes distressed, but Laurie misunderstands the reason for her tears. Afterward, the disappointed Barney avoids the family, but Laurie seeks him out on the day of her wedding. After admitting that he loves her, Barney also intimates that Amy is in love with Alex. Although she is reluctant to believe him at first, Laurie soon realizes that Barney is right about Amy. Thinking that she is doing the best thing for everyone, Laurie sends a cryptic telegram announcing that she has eloped with Barney, which is delivered as friends and family gather for the ceremony. Ernie takes charge, realizing that the family is paralyzed by the news, and announces to the guests that the wedding has been called off. Several months later, Barney and Laurie are living frugally in New York City on the money Barney makes performing in piano bars. Although he has published a few unsuccessful songs, Laurie urges him to finish the song he has worked on since they met. Lacking the money for airfare, Barney misses out on a potentially lucrative opportunity to play with a band in South America. Despite their financial problems and Barney's depression, Laurie has realized that she really loves him, even after he jealously demands that she pawn the bracelet Alex gave her. At Christmas, Barney buys back Laurie's bracelet and they return to the Tuttle home for the holiday. Alex, whose musical has become a success, also joins the family. When they have a moment alone, Laurie returns the bracelet to Alex, but Barney, watching them, thinks Laurie still loves him. Alex has to catch a train, so Barney drives him to the station in Bob's car, dropping Bob off at the drugstore on the way. While returning to the Tuttle house alone through a snowstorm, the depressed Barney intentionally crashes the automobile. Meanwhile, Amy, now engaged to Ernie, confides to Laurie that she once loved Alex, but her feelings changed when she saw how calmly Ernie took care of the family after Laurie eloped. As Laurie laments that she can't make Barney believe she loves him, the Tuttles are informed about the automobile accident involving Bob's car. Believing Bob has been seriously injured, Fran grieves that she has taken her husband for granted. However, at the hospital, they learn that it is Barney who is near death. Weeping, Laurie tells the unconscious Barney that she is going to have his baby. Although the doctor has little hope for him, Barney is taken to the operating room. Over a year later, while he, Laurie and their baby son celebrate Easter at the Tuttle home, the recovered Barney plays his completed song for the family.