In present day (1975) New Orleans, Michael Courtland (Cliff Robertson) is a land developer who is deeply haunted by the past. In 1959, his wife Elizabeth (Geneviève Bujold) and their 9-year-old daughter Amy (Wanda Blackman) were abducted and held for ransom. The police bungled an attempt to rescue them, including a plan involving a briefcase full of blank paper instead of money. In the ensuing chaos, Elizabeth and Amy died. Michael has mourned their loss ever since, even erecting a memorial to them on the land where he'd intended to build a housing subdivision.
On a trip to Italy with his business partner Bob Lasalle (John Lithgow, in his first major film role), Michael revisits the San Miniato al Monte basilica in Florence, where he'd met Elizabeth. There, he encounters Sandra Portinari (also Geneviève Bujold), a local young woman (who speaks perfect English) helping out with the restoration of a painting. She looks exactly like Elizabeth.
Besides looks, Sandra is also similar in personality to Elizabeth, and Michael goes from being intrigued with her to being fixated. He not only falls in love with her, but sees her as a way to redeem himself. He even entertains the thought that Sandra is a reincarnated Elizabeth. Bob and his other associates become deeply concerned when he brings her back to New Orleans with the intention of marrying her. But the reverberations of the past will shake up Michael in a way he never thought was possible.
Any similarities to Vertigo in that plot are strictly intentional, as De Palma once again indulged in his admiration for the work of Alfred Hitchcock, including having Bernard Herrmann write the score. Bouncing back from the failure of Phantom of the Paradise, Obsession became a Sleeper Hit that helped set the stage for the success of his Breakthrough Hit Carrie.
This film contains examples of:
- Altar the Speed: Once he becomes convinced that marrying Sandra is the path to renew his love for Elizabeth, he can't wait to do it.
- Anti-Hero: Michael becomes less sympathetic once Sandra starts bringing out his Necromantic side.
- Batman Gambit:
- It's a complicated scheme, but Lasalle is using Sandra/Amy to manipulate Michael into giving up his money and land. He even comments on how completely Michael fell for the scam and how it made things so easy.
- The ransom plot was actually a failed attempt at this. Lasalle organized the abduction. Knowing how much he loved his wife and daughter, Lasalle expected Michael to pay the ransom, which would force him to give up his share of the partnership. Instead, the police convinced Michael to go along with a phony payment sting operation, which ruined the plan and forced Lasalle to pay the kidnappers off himself.
- Big Bad Friend: Michael never even suspects that his trusted partner Bob Lasalle was behind the kidnapping.
- The Big Easy: Set in New Orleans, with focus on the Southern Gothic side of the city.
- Bittersweet Ending: Having killed Bob, Michael goes off to kill Sandra, but instead finds out that she tried to kill herself, then learns that she's actually his daughter Amy, who didn't really die in 1959.
- Briefcase Full of Money: Subject of the Ransom Drop, from a riverboat on the Mississippi to a dock.
- Chekhov's Gun: A literal gun carried concealed by a waiter at the Courtlands' party, and used for the abduction.
- Chekhov's Hobby: Bob Lasalle's fondness for Italy and his many acquaintances there gives him a place to stash Amy until he can use her in his plot against Michael.
- Cut-and-Paste Note: From the kidnappers.
- Déjà Vu: This was the film's Working Title, and reliving past experiences is major theme for all the main characters.
- Doppelgänger Replacement Love Interest: Sandra looks so much like Elizabeth, it even shocks Bob. Michael falls for her immediately.
- Dream Sequence: Michael dreams about his upcoming wedding to Sandra, where she confirms his notion that he was destined to marry her as a second chance to prove his love for Elizabeth.
- Eiffel Tower Effect:
- For New Orleans, a brief scene in the French Quarter, and some shots of the still-under-construction Superdome.
- For Florence, the exterior of San Miniato al Monte (they weren't allowed to film inside), plus the Ponte Vecchio and other landmarks.
- Every Car Is a Pinto: Elizabeth and Amy die in a car explosion. Well, Elizabeth does anyway.
- Expy: On a basic level as a Vertigo homage, you have Michael/Scottie, Elizabeth & Sandra/Madeleine & Judy, and Lasalle/Elster. There's also a fair amount of Mark Rutland in Michael too, since they have similar names and are both grieving widowers who start an unsettling relationship with a woman he barely knows, to the confusion of his associates.
- Identical Grandson: Sandra looks exactly like her mother Elizabeth did at the same age.
- Internal Reveal: As we see in flashbacks, the lead kidnapper kept Amy in the house, but the others tricked the cops into thinking they'd taken her in the car along with Elizabeth. Bob paid off the surviving kidnapper, then sent Amy to Italy, where she was adopted by Mrs. Portinari and assumed the identity of Sandra, but Michael doesn't learn it until the final scene.
- The Lost Lenore: Michael is despondent over Elizabeth, even after 16 years.
- Manic Pixie Dream Girl: How Sandra comes across at first, but Michael's obsession with her makes her nervous and more serious.
- May–December Romance: Michael, approaching 50, falls for Sandra, who's 25.
- No Indoor Voice: Bob, as fitting his blowhard character.
- One-Word Title: In the Hitch tradition.
- The Oner: Several important shots like this, most memorably when the camera pans back-and-forth between Michael and Bob while they have a conversation over coffee.
- Orbital Kiss: There's no actual kiss, but otherwise the final scene is a perfect example.
- Police Are Useless: The detective's plan to give the kidnappers fake money fails miserably, since they didn't seem to consider that the criminals might actually want to open the briefcase and count the money.
- Ransom Drop: A Briefcase Full of Money gets delivered in a riverboat to a dock in the Mississippi river.
- Red Oni, Blue Oni: Michael is Blue, and Bob is Red.
- Rewatch Bonus: On rewatch, it really becomes an entirely different film. The first time, it's all about Michael mourning for The Lost Lenore and finding a Doppelgänger Replacement Love Interest in Sandra. On rewatch, it turns into the story of Amy reuniting with her father and returning to her long-lost home, and there's added Incest Subtext to Michael's actions.
- Scenery Porn: Much more for Florence than New Orleans.
- Signature Headgear: Sandra's red beret.
- Smug Snake: Even when he just seems like Michael's loyal business partner, Bob has an off-putting, arrogant manner. Turns out he's a Bitch in Sheep's Clothing who's trying to swindle the land away from Michael.
- Stalker with a Crush: Michael starts following Sandra around Florence.
- Stalking Is Love: In Michael's case, love for your dead wife even.
- Surprise Incest: Slightly averted in regards to the Sandra/Amy connection. In the original script, it is made explicit that father (Michael) and long-lost daughter (Sandra) consummate their love affair, but nervous studio executives tried to downplay it by making their wedding into a dream sequence and LaSalle telling Sandra "at least you didn't go to bed with him" as the two board the plane to Rome with the stolen money.
- Time Skip: The first 20 minutes take place in 1959, then the action cuts to 1975.
- What the Hell Is That Accent?: John Lithgow was apparently trying for Cajun with Bob Lasalle's accent, but it's not very convincing and goes from a Foghorn Leghorn drawl to almost vaguely Boston-sounding at times.
- Whole-Plot Reference: Not as slavish a copy of Vertigo as its reputation suggests, but still follows the main outline, with one key scene being a direct lift: the Doppelgänger Replacement Love Interest writes a confessional letter, then throws it away. Marnie also gets referenced, particularly the flashback montage. And of course, the "kidnapped daughter" angle is Paul Schrader doing another Shout-Out to The Searchers.
- You Fool!: Used verbatim by Lasalle during his final altercation with Michael.
- You Killed My Father: The reason why Amy/Sandra went along with Lasalle's scheme, since Lasalle had convinced her that Michael didn't love her anymore and let Elizabeth die on purpose, so she was eager to get revenge on her father.