Grant Jordan, bachelor botany professor, marries Katie, a widow with three kids, despite the machinations of Grant's former girlfriend Minna. But on the wedding day, Aunt Jo, who was to babysit, breaks a leg; so the kids come along on the honeymoon. After misadventures en route, they make it to the Grand Canyon, only to find Minna there, still scheming.

After her longtime rival, Minna Fenster, almost spoils her engagement party, widow Katie Armstrong is distressed to learn that Minna has crashed her fiancé Grant Jordan's bachelor party. Grant, a college botany professor, has proposed the construction of a new botany building on campus, and because Minna, who was once involved with Grant, is the daughter of his influential superior Richard, Grant cannot easily dismiss her. Nevertheless, Grant reassures Katie that he has no interest in the manipulative Minna, while Katie assures him that he will be a good father to her three young children, Abner, Charlie and Zoe. Just before their home wedding, Katie's older sister, Jo Stevens, who is to take care of Katie's children during her honeymoon, trips over Zoe's teddy bear and falls down two flights of stairs. At Jo's insistence, the wedding proceeds, but afterward, she is rushed to the hospital with a broken leg. Unable to find anyone to take care of the children, the newlyweds are compelled to take them on their Grand Canyon honeymoon. During the first night of the hectic train trip, Katie discovers that Abner and Charlie are not on board, having snuck off at Porterville, the last stop. The porter assures the panicked Katie that he will wire the station master at Porterville about the children, and once she, Grant and Zoe arrive at the next stop, Junction City, they can take a cab back. When they get to Porterville, however, they learn that the children took off for Junction City with a traveling salesman. Halfway to Junction City, the cab stops at a gas station, and there Katie finds the salesman, but no children. The salesman explains that after his car broke down, Abner and Charlie hitched a ride with Webb, a local farmer. At the Webb farm, Katie and Grant are finally reunited with Abner and Charlie and spend an uncomfortable night with the family. The next morning, they board the only train available to the Grand Canyon, a day coach. After two more sleepness nights, the Jordans arrive at their Grand Canyon lodge, only to discover that Minna and her father are also there. Just as Grant and Katie are about to embark with the children on a day-long horseback ride, Minna insists that Grant show her father sketches of his botany building, as they are planning to leave for an important college board meeting in California that afternoon. While on the trail, however, Katie bumps into Richard, who tells her that he and Minna are spending the night at the Canyon. By the time Katie and the children return from their excursion, Katie is exhausted, disheveled and furious when Minna coyly extends a dinner invitation. Determined not to appear intimidated by Minna, however, Katie accepts the invitation, then entrusts Grant to watch the children while she has her hair done. Grant, who is soon joined by Minna, struggles to control the rambunctious children and ends up giving the boys a spanking. Katie returns during the punishment and is upset not only by the spanking, but by Grant's admission that Minna was with him. After the newlyweds hurl accusations at each other, Grant storms away in a cab, much to Minna's delight. Grant soon changes his mind, but by the time he returns to the lodge, Katie has checked out. Katie then wires Jo about her imminent arrival, and when she and children arrive home in a cab, a welcoming party is in full swing. Embarrassed, Katie sends the children off in the cab, while she sneaks into her house and tries to talk to Jo alone. Minna and her father then show up, having flown in from the Grand Canyon, and Minna deduces that Katie is hiding. Just as a defeated Katie is about to announce to the guests that she and Grant have separated, Grant appears with the children, who found him at the train station. To Minna's chagrin, Katie and Grant embrace, and the reunited newlyweds finally are able to spend their first night alone together.