Early one morning in the District of Los Angeles Court of General Sessions, Nick Arden (James Garner) appears before Judge Bryson (Edgar Buchanan) so that he can have his wife Ellen Wagstaff Arden (Doris Day) declared legally dead. Five years earlier, Nick and Ellen, who had been married for three years, had been on a plane flying over the South Pacific when a storm caused the plane to crash. Nick and Ellen both made it to lifeboats after the crash, but Ellen was swept off the lifeboat that she was on and neither she nor her body were ever found despite an extensive search and was declared lost at sea. Having spent the last five years searching for Ellen, Nick, who has two daughters, Jenny (Pami Lee) and Didi (Leslie Farrell), has now decided that it's time for him to move on with his life, and part of the reason for having Ellen declared legally dead is so that he can marry a young woman named Bianca Steele (Polly Bergen) later on the same day. Nick plans for his new honeymoon to take Bianca to the same resort in Monterrey where he and Ellen spent their honeymoon.However, on the very same morning, the Navy drop Ellen, who is very much alive, off in Los Angeles, after they have rescued her from the island in the South Pacific where she has spent the previous five years since being swept off the lifeboat. Ellen requests that the Navy do not publicize her rescue or notify Nick about it, as she has plans to tell Nick about it herself. When she returns to her home, she meets Jenny and Didi, but they don't remember her, and she doesn't have the heart to tell them the truth. Her mother-in-law Grace Arden (Thelma Ritter), who is shocked when she sees Ellen, tells her that Nick had just married earlier that morning. Although Ellen is initially crestfallen upon hearing this news, when Grace adds that Nick's honeymoon has not yet started, meaning that his new marriage is unconsummated, it gives Ellen a sense of relief. As his true wife, as opposed to Bianca being his bride, Grace suggests that Ellen should go to the resort in Monterrey and tell Nick that she is alive.Ellen takes Grace's advice, and Nick is just as shocked as Grace was when he sees Ellen for the first time in five years as she confronts him. He is overjoyed at the idea of reuniting with Ellen and wants to stay with her, but Ellen will only agree if he tells Bianca the truth first. Nick returns to Bianca, who is angry and confused, and Ellen follows in order to eavesdrop on their conversation. Although Nick still loves Ellen and wants to be with her more than anything else, he also has to take Bianca's feelings into consideration, which makes him find it hard to tell the truth to Bianca, who is in an amorous mood normally expected of a new bride on a honeymoon. Ellen is irked by Nick's inability to tell Bianca, believing it to be a manifestation of Nick's love for Bianca over Ellen. In anger, Ellen leaves the hotel, but Nick sees her go, and decides to fake an injury in order to stop Bianca from making any more amorous advances.The next day, Nick returns home, where he is told that Ellen was not the only person to be stranded on the South Pacific island - there was also a handsome and athletic man named Stephen Burkett (Chuck Connors) there, and Ellen had given him the pet-nickname of "Adam", while Stephen had called her "Eve". Furious that Ellen mentioned nothing about Stephen, Nick confronts her, and she explains that Stephen is a nerd, and nothing happened between them for the whole five years they were together on the island.Ellen convinces an awkward-looking shoe clerk to pose as Stephen, but Nick is not convinced that the clerk is really Stephen and goes off on his own search for him. When Nick finds Stephen diving from a trampoline into a pool at the Beverly Hills Hotel, he is horrified to find out that Stephen is athletic, attractive and young. Nick invites Ellen to the hotel with the intention of making her confront Stephen. While they are together, Ellen comes clean with Nick about Stephen, though she still swears that nothing happened between them for their entire time on the island and asks Nick for his forgiveness.Nick briefly leaves Ellen after suggesting to her that they go somewhere else, and while she is alone, she notices Stephen. It leads to a confrontation from Ellen, but with Nick instead of Stephen. After she accuses Nick of setting her up with the intent to embarrass her, she storms out of the hotel and drives away. Nick jumps into a taxi to follow Ellen, who tries to evade his pursuit by hiding in a queue of cars at a car wash. The soap and water from the car wash make their way into her car through an open window, and when she tries to escape, she ends up dropping the convertible's top. Nick eventually finds Ellen after the wash is completed, but when he opens the car door, the force of the water that rushes out from inside knocks him to the floor.Back home, Nick finally brings himself to tell Bianca the truth about Ellen, but Grace has him arrested for bigamy as a way of forcing him to choose between Bianca and Ellen. It leads to another chaotic appearance in court with Nick, Bianca, Ellen and Stephen before Judge Bryson, the same judge who had earlier married Nick and Bianca but is now even more confused because he has four matters to deal with - the charge of bigamy against Nick, Bianca's request to annul her marriage to Nick, and two requests from Ellen, one to make her death certificate null and void, and the other to divorce from Nick. In the end, Bryson dismisses the charge of bigamy, grants Bianca's request to annul her marriage, declares Ellen alive again and postpones his judgment on the divorce proceedings between Ellen and Nick, before sending all of the parties away. Bianca leaves Nick outside the court, and Ellen, who is still legally married to Nick, storms out of the courthouse after rejecting an invitation to have lunch with Stephen.Ellen returns to her home and starts to search for Nick. Grace, who had expected Ellen to be back hours before, finds her and tells her that after she stormed out of the courtroom, Nick caught a taxi. Worried that she has messed things up, Ellen asks Grace about the children, and she replies that they have had to live without their mother for a long time, so she supposes that they could do without their father around the house. When Ellen asks Grace how she will speak to them, Grace tells her to march herself outside and tell them who she is.After taking off her coat, Ellen goes outside. She doesn't see anyone at first, but then Jenny and Didi reveal themselves to be swimming in the pool, and they both refer to Ellen as "Mum" or "Mummy". After Ellen looks back at Grace, who has followed her out, she hears another splash and sees that Nick is in the pool as well. Nick says to Ellen "Well, isn't it about time somebody started kissing somebody around here?" Ellen runs to Nick, and they hug each other, sending Nick falling backwards and pulling Ellen into the pool, where they kiss and play with the children.