Sir John Carteret (Howard) is an English lord who, in 1898, still mourns his lost love, the ridiculously named Moonyeen Clare (Shearer), who tragically died thirty years before. His good friend Dr. Owen brings to him Moonyeen's five-year-old niece Kathleen, orphaned after her parents were killed in a shipwreck. Sir John is reluctant but after meeting the girl, takes her in as his ward.
Cut forward to 1915 and Kathleen is a grown woman (also played by Norma Shearer). She has a Meet Cute with a handsome young American, Kenneth Wayne (March), who has inherited the neighboring property, and has arrived in England as a volunteer joining the British Army for World War I. Sir John is utterly horrified to hear this, and is forced to tell Kathleen the story of her aunt's death. Turns out that Moonyeen was murdered during her wedding to Sir John, fatally shot by a rejected suitor — Kenneth Wayne's father Jeremy (also played by March).
Smilin' Through was an adaptation of a stage play. It had been previously adapted as a silent film in 1922 and was adapted again in 1941 as a vehicle for Jeanette MacDonald.
- Blood-Splattered Wedding Dress: Moonyeen takes her hand off her dress to reveal a bloodstain after John shoots her in the stomach.
- Childhood Marriage Promise: It seems one was made in the backstory between Moonyeen and Jeremy. Jeremy is very angry that the promise isn't being fulfilled.
- Conversation Cut: At Kathleen's birthday party, Dr. Owens starts making fun of her earnest but super-dull suitor Willie. There's a close-up of Kathleen's face, then a cut to a more distressed Kathleen in the rain as Willie says "Look here old girl, you know I can't talk the romantic stuff."
- Dances and Balls: Sir John hosts a grand ball the night before his wedding to Moonyeen. This is where its established that Jeremy was thrown over for John and is none too happy about it.
- Have a Gay Old Time: "I came back alone to this house, all gay with flowers for her."
- Heartwarming Orphan: Aging bachelor Sir John initially says he will absolutely not take a child into his home. But one little look at adorable five-year-old orphan Kathleen, and he's offering her a place to stay.
- He's Dead, Jim: Dr. Owen doesn't even examine Moonyeen, just taking one look after he's shot and shaking his head negatively when Sir John asks for his help.
- Identical Grandson: Kenneth looks exactly like his father. But that isn't the worst example—see Uncanny Family Resemblance below.
- If I Can't Have You...: Jeremy says words to this effect, saying "The man doesn't live who can take you from me—the man won't live who will take you from me" during his final confrontation with Moonyeen in the garden. He makes the same kind of remark just before he shoots her.
- I Have No Son!: Sir John tells Kathleen that if she goes away with Ken she can't ever come back.
- Karma Houdini: Jeremy Wayne, who murdered Moonyeen in front of a crowd of witnesses, somehow escaped, making it to America and having a son.
- The Lost Lenore: Sir John spends fifty years mourning for Moonyeen after her death. He's violently angry when the son of Jeremy Wayne enters his life.
- Match Cut: From Ken and Kathleen embracing alongside his car to Ken and Kathleen embracing at the train station as he's going away to war.
- Meet Cute: Kathleen and John meet for the first time when they separately enter the abandoned guest house to take refuge from a driving thunderstorm.
- A Minor Kidroduction: We first meet Kathleen when she is brought to Sir John's home as a five-year-old.
- Not Named in Opening Credits: It was MGM house style at the time to never credit two parts to actors who play double roles. So the opening credits list Shearer as Kathleen only, and March as Kenneth only, with no credit for Moonyeen or Jeremy.
- Pun: After Kathleen and Willie take refuge from a storm in the abandoned guest house, they meet Ken, who also comes in. Ken digs up a bottle of 1847 port from the cellar, says "Any old port in a storm, eh?", and laughs.
- Redemption Equals Death: Sir John, who has held hate in his heart for Jeremy Wayne for fifty years and has violently opposed Kathleen's marriage to Ken for four years, finally softens, and consents, and asks Kathleen to bring Ken over. Minutes later, he sits down to chess with Dr. Owen and dies.
- Separated by a Common Language: Kathleen and Ken are constantly correcting each other's accents—she dings him for his flat "a" in "ghastly" and his long "i" in "neither", and he later gets her for her pronunciation of "after. Also, apparently Americans called doughnuts "sinkers" in 1915, as Frederick does, only to be corrected again.
- Smart People Play Chess: Dr. Owen and Sir John, members of the British upper crust, like to while away their time by playing chess.
- Time Skip: A scene at Kathleen's sixth-birthday party in 1898 focuses in on the cake, then cuts to another cake at Kathleen's 23rd birthday in 1915.
- Titled After the Song: Before the play or the movies there was the 1919 song "Smilin' Through."
- Title Drop: Moonyeen sings the song "Smilin' Through" at the pre-wedding reception.
- Together in Death: Sir John dies. His ghost, looking as he did in youth, rises from his body and reunites with the ghost of Moonyeen. They then have the wedding in the afterlife that they never got to have living, complete with Moonyeen throwing the bouquet to the ghosts of her friends.
- Uncanny Family Resemblance: Moonyean looks exactly like her niece, Kathleen, except that Moonyean was a blonde while Kathleen is a brunette.
- Widowed at the Wedding: Jeremy murders Moonyean during her wedding to Sir John.