Harry (Edmond O'Brien) and Eve Graham (Joan Fontaine) want to adopt a child, as Eve is infertile. Adoption agent Mr Jordan (Edmund Gwenn) warns the couple that he would need to investigate them thoroughly. Harry looks curiously at Jordan, something that worries Jordan.
Johnny Case (Cary Grant), a self-made man who has worked all of his life, is about to marry Julia Seton (Doris Nolan), whom he met while on holiday in Lake Placid, New York. He knows very little about his bride-to-be, and is flabbergasted to learn that she is from an extremely wealthy family, the daughter of banker Edward Seton (Henry Kolker). He meets Julia's vivacious sister Linda (Katharine Hepburn), to whom he confides his plan to take a long holiday from work to find the meaning of life, and also meets the sisters' dissolute brother Ned (Lew Ayres), whose spirit has been broken by subservience to his father. At first, the father is stunned when Julia tells him about her plan to marry Johnny, but he is appeased after meeting him and looking into his work history. Julia makes plans for an elaborate New Year's Eve engagement party, even though she promised Linda that she could throw Johnny and Julia a smaller, more personal affair that would include only close friends.
Walter Burns (Cary Grant) is a hard-boiled editor for The Morning Post who learns his ex-wife and former star reporter, Hildegard "Hildy" Johnson (Rosalind Russell), is about to marry bland insurance man Bruce Baldwin (Ralph Bellamy) and settle down to a quiet life as a wife and mother in Albany, New York. Walter determines to sabotage these plans, enticing the reluctant Hildy to cover one last story, the upcoming execution of convicted murderer Earl Williams (John Qualen).
Dans le petit village de Trémolat, dans le Périgord, on célèbre le mariage de l'instituteur Léon Hamel avec une jeune femme du village. Parmi les invités de la cérémonie, la jeune collègue de l'enseignant, Hélène David, qui est également la directrice de l'établissement scolaire et Paul Thomas, surnommé « Popaul », le boucher du village.
La princesse Charlotte, héritière d'un petit royaume d'opérette, est de passage à Paris avec son royal père et toute la suite de ce dernier. Dans la capitale, ils donnent un dîner prestigieux, à la veille du mariage de Charlotte et du grand-duc Guillaume de Spartz-Hohenburg. Lors de cette soirée, Charlotte est remarquée par Paul, un play-boy noceur. À la suite d'un pari avec sa bande de copains, il use de son charme et attire la princesse jusque dans son lit. Alors que cela ne devait être qu'une passade, Paul tombe amoureux de la princesse, et dévoile malgré lui les photos du scandale dans la presse afin de régler une importante dette de jeu…
While on a cruise, stodgy, overly-frugal businessman Larry Wilson (William Powell) gets hit on the head with an oar while rescuing 'Doc' Ryan (Frank McHugh). He wakes up and remembers that he is actually a suave conman named George Carey; Doc is one of his crooked associates. However, he has lost all memory of the past nine years as Larry.
Vicky Lowndes (Jean Arthur) loses her first husband, Bill Cardew (Fred MacMurray), in a boating accident in which he is presumed drowned. The lonely widow is comforted by Bill's best friend and publishing business partner Henry Lowndes (Melvyn Douglas). Six months later, she marries him. Six months after that, Bill shows up, after having been stranded on a uninhabited island and then rescued. Vicky has a tough choice to make. Hilarity ensues.
At the suggestion of one of her friends, Jill Baker (Merle Oberon) visits psychoanalyst Dr. Vengard (Alan Mowbray) for her intermittent hiccups, which appear when she gets nervous or irritated. He soon has her questioning her previously happy marriage to her business executive husband Larry (Melvyn Douglas).
Jean Harrington (Barbara Stanwyck) is a beautiful con artist. Along with her equally larcenous father, "Colonel" Harrington (Charles Coburn) and his partner Gerald (Melville Cooper), she is out to fleece rich, naive Charles Pike (Henry Fonda), the heir to the Pike Ale fortune ("The Ale That Won for Yale"). Pike is a woman-shy snake expert just returning from a year-long expedition up the Amazon. Though surrounded by ladies desperate for his attention, Charles is putty in Jean's hands.
Ils ont 25 ans et se marient aujourd'hui. Ils ont 35 ans, se sont unis il y a dix ans et se déchirent aujourd'hui. Ils ont 45 ans, se sont déchirés il y a dix ans et tentent aujourd'hui de se réconcilier... Trois mariages dans un mariage, trois couples durant les 24 heures d'une noce quelque peu perturbée par les doutes et les crises de chacun. "Qu'il est formidable d'aimer", chante courageusement le curé, à l'heure où un mariage sur trois se termine en divorce... Un sur trois : d'accord, mais lequel ?
Clara et Ismaël vivent un amour heureux, sans se soucier du fait qu'elle soit juive et lui musulman. Mais lorsqu'elle est enceinte, les réactions de leur entourage changent la situation.
Vingt ans après avoir été adopté par une famille suisse, les Depierrat, Vinh va épouser Sarah dans l'intimité pour éviter que ses parents adoptifs Claire et Michel ne se recroisent, la famille ayant éclaté depuis dix ans.
Justine est une journaliste à la télévision, et sa rencontre avec Djalil, chirurgien provoquera un coup de foudre entre eux. Ce coup de foudre sera aussi source d'étincelles entre eux, et leur famille.