The film starts by showing us a man (Robert Neff) sitting in a large car parked off to the side of the road, engine still running, though. We're shown the mile marker (3.5) he's parked at; the man looks at his watch. It is precisely 8:30. He's obviously waiting for someone.
Then we see a car approaching up a winding road. It contains Jane and Alan Palmer (Lizabeth Scott and Arthur Kennedy) on their way to a party in the Hollywood Hills, hosted by Alan's boss and his wife. Jane Palmer begs her husband Alan, who is driving the couple's convertible, to turn the car around. When she explains that she cannot face the party's hostess and her condescending ways, Alan turns the car around only after he and Jane argue. In the course of the argument, Jane reached for the ignition keys. Instead, she hit the headlight switch, turning off the headlights, which Alan then turned back on. We see the man in the waiting car drive it unto the highway toward Jane and Alan's convertible.
As Jane and Alan's convertible passes the oncoming car, the driver tosses a large satchel into the back seat of their car. The driver had interpreted their blinking headlights as his signal. After stopping briefly to examine the suitcase and discovering that it contains bundles of money, Jane and Alan see another car approaching theirs at a fast speed. Jane urges Alan to get into the car and then, behind the wheel herself, she drives on. A chase ensues, with the car pursuing Jane and Alan until, after a dangerous drive, Jane finally is able to give the pursuer the slip. Obviously, the car pursuing Jane and Alan's vehicle is the one into which the satchel should have been thrown. And it is possible that the driver of that car now has the license plate number of Jane and Alan's car and will be able to trace them.
Back in downtown L.A., Jane and Alan are stopped by a police officer who writes Alan a ticket for making a turn without signaling. The police officer notices the two are nervous. Jane tells him she and Alan are eloping to Las Vegas.
When Jane and Alan get back to their apartment in Chateau Michele, Alan wants to turn over the money to the police and be done with it. Jane sweet talks him into delaying that.
Alan's sister Kathy Palmer (Kristine Miller), who has Apartment 515 across the hall, comes into their apartment, even though it is late. Alan pleads a headache and Kathy leaves, but this scene serves to introduce Kathy, her close relationship to Alan, and her dislike of Jane.
After Kathy goes, Jane and Alan agree to check the bag at Union Station for a week. Alan and Jane go to Union Station and check the satchel, for which he receives a claim ticket. To draw viewers' attention to the checkroom claim ticket, Alan at first appears to have lost it, until he reveals that it's fallen through a hole in his overcoat pocket and into the lining of the coat. He retrieves it. Alan later places this ticket in the drawer of a chest of drawers in the bedroom under his service revolver, though Jane doesn't know he's put the ticket there.
The next day Jane goes on a shopping spree, purchasing $780.00 worth of clothing, among which is a fur jacket. Alan learns of this when his bank calls to tell him that Jane has written checks for large amounts. When Alan comes home, he and Jane argue again because Alan wants to turn the money over to the police. Alan brings up Jane's first husband, a man named Blanchert, whom she married for his money. Jane tells Alan that growing up she was white-collar poor, that she lived among middle-class people but her family never had enough to keep up. This explains Jane's attitude toward money. To appease Alan, Jane agrees to his plan to duplicate the events of their first date.
Earlier that day after Jane returned from shopping and before Alan came home, small time hood Danny Fuller (Dan Duryea), posing as a detective, arrives at the Palmers' apartment (having traced their car's license number) and asks to search the place, even though he doesn't have a warrant. When Jane allows the search, Danny knows she has the money, otherwise, as Danny says, she would have screamed for the police and tried to throw him out. Danny demands that Jane give him the suitcase. Jane lies, telling Danny that they have already turned it over to the police; Danny leaves but threatens to return if news of a suitcase full of money being turned over to the police does not appear in the afternoon's newspapers.
To duplicate their first date, Alan and Jane make plans for dinner and a boat ride at a nearby lake the next night. Before Jane and Alan "date," while Alan is out, Danny returns, knowing now that Jane lied, but Jane persuades him to split the money with her. She tells Danny she can take him to the money. She still hasn't revealed to Danny that it's in the satchel at the Union Station checkroom.
Of course, Jane has to get the money, and to get that, she must locate the claim ticket. Jane tells Danny to meet her later that night at a palm tree at the west end shore of the lake where she and Alan are going for a boat ride. When Jane goes to meet Alan for dinner, she takes his gun from the dresser drawer because she is planning to kill Alan and dump his body in the lake.
After dinner, Alan and Jane take a motorized boat onto the lake. But Jane loses her nerve; she asks Alan to go back to shore, but Alan says no, they've just come out unto the lake. Alan wants a cigarette and is about to open Jane's purse, when she strikes his hand, stopping him. Alan asks her what's in the purse; it's so heavy. And at that point, the gun falls out of the purse. The two grapple for the gun, and it goes off, killing Alan.
With Alan's dead body in the boat, Jane then steers the boat toward the palm tree and picks up Danny, who is stunned to discover Alan's corpse in the boat. He's going to back out; he wants no part of murder. But, seeing he hasn't any choice, Danny helps her dump Alan's corpse overboard, after first securing the corpse so it won't rise to the top.
Before putting Alan's body into the pond, Jane took off his overcoat and his hat, and Danny put them on. When the boat pulls up to the dock, Danny gets out, keeping his face and body turned away from the boat rental agent (Billy Halop), while Jane pays. He hurries off, and Jane rushes to catch up with him.
Together Jane and Danny drive back to Jane's apartment house where Danny drives the car into the basement garage, according to their plan to convince Pete (Smoki Whitfield), the black garage attendant, that Alan is still alive. Once the car is in the garage, Jane gets out, and Danny drives the car out of the garage, but not before Jane calls Pete's attention to herself and "Alan." She tells Pete "Alan" wants the car washed when he brings it back. As "Alan" drives out of the garage, Jane shouts after him, telling him to purchase some cigarettes for her at the drug store. Thus, it appears that "Alan" is going on an errand of some sort and will get the cigarettes on the way.
Once upstairs, Jane knocks on Kathy's door and asks her to come over for a nightcap. Jane tells Cathy that Alan has gone out to get a bottle and some cigarettes, and Kathy says she will stay for a drink. When Alan doesn't come home after several hours, Jane acts worried and eventually phones the police to report Alan as a missing person. In the course of this time, the nervous Jane asks Kathy to fix them both a drink, whereupon Kathy discovers that there is plenty of liquor under the kitchen sink. So why is Alan going out for a bottle? Further, Jane tells Kathy she's sure that Alan doesn't love her anymore, that he's involved with another woman, which Kathy dismisses as nonsense, though this does arouse her suspicions further. Why is Jane telling her this?
After Kathy leaves, Jane leaves to keep an appointment with Danny. She still believes he has the claim check in the lining of Alan's overcoat. At the motel unit where Danny is renting a room, they inspect that lining of the coat and Danny brings out the claim check--only it isn't the claim check. It's a blank piece of paper. Alan, suspecting Jane would try to claim the money behind his back, had replaced the claim check with this blank and put the original claim check in his dresser under his revolver.
Jane now comes clean and explains to Danny where the money really is and how they must find the actual claim check ticket in order to get the money. In the motel room, Danny tries to kiss Jane, saying he wants to know Jane better. She momentarily resists him but then embraces him, kisses him, and the scene fades out. I deduce the two have sex. The fade-out used here was common in films of the 40s to indicate a sexual scene. Also, from their very first meeting, Jane had been trying to lure Danny into sex, which, at that time, Danny wasn't interested in.
The next morning, still worried about Alan, Kathy uses her passkey to enter Jane and Alan's apartment. She searches through various items of furniture, coming at last to the chest of drawers in the bedroom. There she discovers that Alan's revolver is missing. And underneath the cloth upon which the revolver rest, Kathy discovers the claim check for the satchel, which she takes--steals. Jane, of course, is unaware the claim check was there.
The next morning when Kathy asks about Alan and learns he's still missing, Kathy suggests they look for Alan's revolver. It was one of his favorite things. If Alan were planning to run away, surely he'd have taken it. But they find it in the dresser drawer, where Jane put it when she returned home the previous evening.
The police cannot act upon Jane's report of Alan as missing. Alan hasn't been gone long enough and, besides, there's no evidence of a crime or foul play. Nonetheless, Jane continues to play the role of distraught spouse, worried over a missing husband.
It's apparent that Jane and Kathy don't like each other, and Kathy begins to be suspicious of Jane. She's also aware that Danny (whom she doesn't know by name) has come to Jane's apartment.
Just as Kathy leaves Jane's apartment, she opens the door to find a man standing there, about to knock. This man identifies himself as Don Blake (Don DeFore), who says he's Alan's friend and a fellow war veteran. Don says Alan told him to drop by if he were ever in L.A. Don is in L. A. for a vacation and decided to look up Alan. Kathy takes him into her own apartment and explains that Alan has just recently gone missing. She tells Blake of her suspicions about Jane. This makes Kathy and Don Blake a team investigating Alan's disappearance. At the film's denouement, we learn why Don is only too willing to believe the worst of Jane.
Later, Kathy introduces Jane to Blake. Jane asks Blake some questions about his war service with Alan and is immediately suspicious when Blake gives her erroneous answers. After Blake and Kathy depart, Danny arrives.
Jane tells Danny that she has the money, and they will go to get it. In reality, she is planning to drive Danny into the Hollywood Hills and shoot him to death with Alan's gun. Jane drives recklessly, and Danny becomes increasingly suspicious and unnerved. After Jane narrowly avoids a collision, Danny demands that she stop. He tells her she's lying when she says the money's buried in the hills, and he gets out of the car and walks away. As he disappears, Jane cries to herself, "The claim ticket is in that coat," because she thinks the claim ticket is still in the lining of Alan's coat, which Danny is wearing. She must now get that coat back from Danny. Jane drives to the beach and abandons her car. Two vagrants (Richard Irving and Jimmie Dodd) steal it and drive away in it. They abandon the car near the Mexican border.
Jane visits Danny at his place to reclaim the coat. This arouses Danny's suspicions, and he begins to search the coat. In the lining he finds--what?--NOT the claim ticket but a blank bit of paper about the size of the claim check ticket. Alan, again not trusting Jane, had substituted the blank for the real ticket. Jane now comes clean and explains to Danny where the money really is and how they must find the actual claim check ticket in order to get the money. Jane and Danny have sex as her way of luring him on to trust her.
When Jane returns to her apartment, a Lt. Breach (Barry Kelley) shows up, saying he's investigating Alan's disappearance. Kathy is also there. Lt. Breach tells Jane, "There's another woman" and details the near accident that occurred when Jane was driving Danny into the Hollywood Hills a night earlier. The driver of the car Jane almost hit obtained the license number of her car, thus Breach says it was Alan and Jane's car. Lt. Breach says the other woman (in fact Jane herself) was driving and Alan (Danny dressed in Alan's coat and hat) was the passenger. Instead of acting surprised and stunned at this news, Jane says she knew there was another woman and gives a bit of description of this woman, saying she'd only seen her from a distance. Kathy who's listening to all of this, is confused and suspicious; Alan just couldn't be committing adultery; not her brother!
Suspicious of Don and his story of being Alan's war buddy, Jane phoned Jack Sharber (David Clarke), a friend of Alan's with whom she is acquainted. When Sharber tells her that he does not recognize Blake's name as belonging to a member of their war unit, she invites Sharber to the apartment the following night to meet Don Blake.
Later, Jane and Danny meet again. Jane explains that Kathy has become too suspicious of her and feels that Kathy will discover their plot. Jane asks Danny to buy her some poison so that she can kill Kathy, making it appear a suicide, i.e., Kathy and Alan were close; Kathy was despondent over Alan's disappearance; therefore, Kathy commits suicide. Danny agrees to do this, though he doesn't like it but says he's too far in to back out now.
Knowing Jane is out of her apartment, Kathy, using a key she has to Alan and Jane's apartment, enters the apartment. She begins a search of the apartment and discovers that Alan's revolver is missing. She also notices the claim check ticket, which was under the cloth in the drawer where the gun had been kept. Jane is obviously unaware of this or she wouldn't be searching for the ticket in the coat lining. Without a qualm, Kathy takes the ticket! This was stupid thing to do. Certainly, had Jane known of the ticket, she would immediately notice the missing ticket and deduce that Kathy has been in the apartment.
Later, Blake arrives to pick up Kathy for a date, and she gives him the claim check ticket. They agree to stop at Union Station before going to dinner and present the claim check ticket to see what is there. But as they leave Kathy's apartment, Jane demands that they come over to her apartment, where Sharber is waiting. When Sharber says that he does not recognize Blake, Blake realizes that his phony story of being Alan's war buddy is unfolding as a lie. When Sarber goes, Jane, in a take-no-prisoners situation, pulls her gun and demands that Don give her the claim ticket. Kathy, now suspicious of Blake herself, because he lied about being Alan's buddy, runs into her apartment to phone the police, hoping they will arrive to straighten everything out. When Kathy returns to Jane's apartment, she finds Don unconscious on the floor and Jane gone. Kathy once again phones the police and tells them to go to Union Station. Now that she has the claim check ticket, Jane has gone to collect the satchel herself.
At Union Station, Jane decides not to collect the suitcase herself. Instead, she gives a come-on to a lonely guy (Denver Pyle) near the newsstand and asks him to reclaim the bag for her in return for $5. She also promises him that, if he wishes, he can later spend that $5 on her. Thinking he's unto a potential one-night stand, the guy gets the suitcase. But when he reads the tag on the satchel's handle, he sees there is a note there that Alan had written: "If a woman tries to claim this suitcase, call the police." This is a further indication that Alan didn't trust Jane. The lonely guy gives the suitcase to Jane and takes off; he's not going to tangle with this dame.
Jane goes to Danny's apartment, where she finds Danny quite drunk. She displays the satchel and the money to him. She then asks him to explain what the blackmail money was paid for. Danny explains that he stumbled unto a fraud. A wealthy L.A. insurance agent, who provided insurance on bridges, actually never took out the policies. Instead, because bridges rarely fall apart, the agent simply took the annual payments on the policies and kept the money for personal use. Danny blackmailed the man; the $60,000 was Danny's blackmail payoff. Jane is overjoyed, for she now knows the money is not marked and they can spend it. She suggests that they drink a toast before heading off to Mexico together. But Jane slips some poison (which Danny had bought earlier for Jane to use on Kathy) into his drink, and he dies.
Meanwhile, Don has explained to the police his suspicions about what's going on, and they agree to call on Danny. Just ahead of the police's arrival at Danny's place, Jane flees to Mexico. The police discover the dead Danny and conclude he committed suicide. Jane had arranged Danny's hand on the poison bottle before she left the room. The police talk to Danny's girlfriend (June Storey) who's just arriving at Danny's room. The girlfriend explains that she was with Danny when he bought the poison, that she knew Danny had some sort of big deal on but didn't know the details of it. And the police use her testimony to bolster their conclusion about Danny committing suicide. When Don arrives at Danny's room, he tells Lt. Breach he's sure Jane is responsible for Danny's death and Alan's death and that Alan's body is in the lake, but Breach dismisses Don theory as nonsense and refuses to drag the lake because he doesn't have enough evidence to go on to conduct such an expensive and time-consuming operation.
We see Jane speeding along a road in Mexico; she stops to transfer the satchel of money from the back seat of her car to the trunk. A stranger in a cowboy hat (George Mann) stops and offers Jane aid. When he notices a large bill on her bumper, he suddenly develops other ideas. But before the guy can do anything to Jane, a police car drives up, and the officer (Alex Montoya) asks her if anything is wrong. Jane calmly says, "No. I just finished changing a flat tire." She drives off.
Once in Mexico City, Jane checks into a lavish hotel and hides the suitcase containing the $60,000 in her room. She buys herself some fancy clothes, joins the hotel's social whirl, and is soon being escorted by Carlos (John Mansfield), a smitten Latin lover. Thinking all is going her way, she is upset to discover Don Blake knocking at her hotel room door. When he barges in, Blake accuses her of murdering Alan and of being in Mexico with the money. He leads her to believe that Alan's body has been found in the lake. Don cons Jane into showing him the suitcase of money by saying he'll let her alone if she gives him half the money.
Once he's seen the suitcase, he reveals that he is actually the brother of Jane's first husband, Blanchet, and says that he never believed the report he'd received when he was in the Army that his brother had committed suicide, but rather, he had always suspected Jane of murdering him. But then he reverses himself and says that perhaps his brother did commit suicide but only because of the heartless way Jane treated him. Blake calls the police, waiting in the hotel lobby, whom he'd already alerted to what he was doing. Overwhelmed by panic and dismay, Jane backs away from Blake. As the police come into her hotel suite, Jane bumps into the balcony railing outside her suite's living room doors and falls from the balcony to her death below.
In the lobby, we see Blake and Kathy together. They had married a few days earlier, and Blake tells her they will go home, that their honeymoon has been a short one.