It is the whimsical story of a starchy English banker and his madcap aunt. One Henry Pulling (Alec McCowen) is the starchy banker, a fellow who can rattle off the pound's conversion to dollars, francs, and lira off the top of his head, and who has no interests other than the dahlias in his garden. Henry is attending his mother's funeral when his long-lost – and believed dead – Aunt Augusta (Maggie Smith, buried under tons of old-age makeup) shows up, much to his surprise.
Augusta is eager to make a connection with the nephew whom she hasn't seen in decades. However, the reunion is soon disturbed when Augusta receives a grisly package: the severed finger of her old boyfriend and true love Ercole Visconti (Robert Stephens), a roguish Italian who is being held hostage by Mafia gangsters. Augusta goes on a wacky trans-European quest to raise the £100,000 she needs to liberate her beloved Ercole, with Henry unwillingly tagging along.
Tropes with My Aunt:
- Briefcase Full of Money: Augusta tries to earn the first chunk of the £100,000 she needs to liberate Ercole by...joining a scheme to smuggle £50,000 through Europe to Turkey and a general plotting a coup. Henry is shocked when he finds out what's in the red briefcase.
- Call-Back: The first shot of the movie is a closeup of a nude painting of Augusta. Later it turns out that the painting is a Modigliani and is worth a fortune.
- Clown Car: In a voiceover Augusta says Achille had a wife and two children. This is followed by a shot of Achille, his wife, and their six children all getting out of a pretty cramped elevator.
- Diabolus ex Machina: Augusta gets all dolled up to meet her old lover Achille, who has enough money to pay Ercole's ransom and get her out of her fix with the money smugglers. He's happy as can be to see her again, and it seems her troubles are over. Then Achille dies of a heart attack that very night. (Not Out with a Bang, though.)
- Faked Kidnapping: It turns out that Ercole was never kidnapped. It was all a scam by Ercole to get £100,000 from Augusta. She still carries a torch for him and she is heartbroken when she finds out.
- Family Relationship Switcheroo: It isn't hard to guess, given how in the first scene Augusta tells Henry that he was adopted. Sure enough, the ending reveals that Henry is Augusta's son, whom she gave to her sister to raise.
- Finger in the Mail: Augusta receives first a finger and then an ear of Ercole's, sent in the mail by the gangsters who have kidnapped him.
- Flashback: Maggie Smith gets to take off the old-age makeup for a series of flashbacks. The first couple demonstrate how roguishly charming Ercole got her to leave a school tour group to become his lover. A couple more flashbacks show Augusta as a High-Class Call Girl, then show how she became the mistress of a rich French businessman named Achille.
- Funny Foreigner: In one of his first film roles, Louis Gossett Jr. (already bald in 1972) plays "Wordsworth", Augusta's younger lover from Sierra Leone. He speaks with a thick accent, and much confusion happens in one scene where Wordsworth confuses "cannabis" for "cannibal".
- Hey, Wait!: A terrified Henry is trying to get the red suitcase with £50,000 in it past French customs. He is about to pick the suitcase up when the customs guard says "Un moment." As Henry stands rigid, the guard simply writes a check on his red suitcase with chalk.
- High-Class Call Girl: What Augusta was in her youth, after she was deflowered by Ercole in Paris. Apparently the last time she saw him she was already a hooker in a fancy brothel.
- Intoxication Ensues: Henry smokes a joint thinking it's a tobacco cigarette. He gets very high.Henry: Are these herbal?
- The Ken Burns Effect: The first shot of the movie is a slow pan over what turns out to be a nude painting of Augusta in her youth. The painting becomes important later.
- Left Hanging: Literally! At the very end Henry offers to flip a coin with his mother: if he wins, she'll retire to a quiet life in England with him, and if she wins, he'll join her on madcap globetrotting adventures. They flip the coin, it flies up into the air, and the film ends with a freeze frame of the three of them (Henry, Augusta, and Wordsworth) looking up at it.
- Meet Cute: Achille meets Augusta in a Flashback where she's knocked off her horse after nearly colliding with her car. As soon as he's confirmed she can stand up, he's whisking her back to the hotel for sex.
- The Mistress: In the backstory, Augusta was this for rich Achille for a while, until both Achille's wife and Achille's other mistress find out.
- Nephewism: After the death of his mother a staid Englishman goes off on an adventure with his madcap aunt.
- Orient Express: Henry and Augusta take the Orient Express to Istanbul. When he goes to bed with Tooley the hippie girl, Henry gets into the spirit of things, saying "After all, this is the Orient Express."
- Road Trip Plot: Henry and Augusta, gallivanting around Europe while she tries to raise a bunch of ransom money.
- Sure, Let's Go with That: Augusta is trying to delicately tell Henry that she was a High-Class Call Girl, but he misunderstands her. (Later he does find out the truth.)Augusta: It was known as "La Quintilian."
Henry: You were in a theater company!
Augusta: Uh, that description will serve.
- Toplessness from the Back: A random stripper at the club where Henry meets Wordsworth.
- Uptight Loves Wild: It's a platonic, family example. But the plot hits all the other beats of Uptight Loves Wild, with a starchy, fussy man being dragged into wacky, messy adventures by his wild and free-spirited aunt.