Examples of Foreshadowing in Knives Out.
- At the start, when Fran discovers Harlan's body, she almost drops the tray but catches herself in time, subconsciously stopping herself from doing something unprofessional - a subversion of the usual 'drop what is being carried on seeing the dead body' schtick. This foreshadows that Harlan's staff are consummate professionals who can do their job effortlessly and do the correct thing subconsciously. Which comes up later on when Marta negates Ransom's switching of the vials by subconsciously picking the one with the right medication, and only thinks she got it wrong when she sees the label.
- When Linda is asked about her relationship with Harlan during the initial interviews, she says that you have to know how to make things a "game" with him and that they have a long history of doing so with each other. This is a big hint about the letter he threatened her cheating husband with. He opens it and dismisses it as a blank sheet of paper and an empty threat, so he thinks no more about it. She recognizes immediately because she's received other messages from Harlan in invisible ink beforenote and automatically exposes it to heat to reveal the message.
- Marta brings up the signs of a deadly overdose of morphine when she realizes that she just gave Harlan over thirty times the normal dose. However, even as the minutes pile up, Harlan doesn't demonstrate any of the symptoms, even the initial ones. Sure enough, the toxicology report comes back clean, and Marta did not administer an overdose despite the switched fluids.
- Marta is a nurse and is competent — knowing all Harlan's meds and dosages (even quasi-legal ones) by heart. Any medically trained personnel worth their salt wouldn't have misplaced the emergency kit containing the antidote, especially when kits are (A) very obvious, and (B) have a compartment that would make it clear someone tampered with the most important of the meds. Sure enough, Ransom had sabotaged her med kit to steal the antidote.
- When Marta and Harlan play Go, she tells him that she always beats him because he plays to win, and she plays to make a beautiful pattern. Several times Marta unknowingly foils Ransom's plans by being a good and kind person rather than acting as selfish as the rest of the family.
- Harlan makes a crack about knowing a real knife from a prop knife. In the end, Ransom tries to stab Marta, but discovers that he's using a prop knife.
- Ransom forces all the Thrombeys' employees to call him "Hugh" because he is an asshole. This hints at the fact he is just as classist and unpleasant as the rest of the family, with his kindness to Marta being an act.
- None of the family members would have profited at all from Harlan's death, because that would mean losing their income. Ransom is the one with the least stakes out of the family, and thus, has no such compunctions killing Harlan.
- At the will reading, Ransom smirks whilst playing with a chessboard. He's 'The Chessmaster' of the film; the one who orchestrated the entire plot to kill Harlan and frame Marta for it.
- Chess is also a game you can only win by playing to win. When he is in control, he can manipulate Marta effortlessly, but whenever she acts on her own, playing her game her way, she sticks to the beauty and benevolence of her style of Go.
- As Blanc is going over certain events on the night of Harlan's death, he says that during the night, Meg woke up from the sound of the family dogs barking. This is one of the only details that isn't explained by the flashback of Marta covering up Harlan's death since the dogs liked her enough to be silent when she was sneaking through the yard. He later discovers that they were barking at Ransom, who was trying to sneak in to switch back the medication bottles. They even bark when he arrives and steps out of his car, and for no other family members.
- Ransom says that he thought he was the only one who ever beat Harlan at Go. This sets up the final confrontation between Ransom and Marta, showing that she is smarter than he is and allows her to trick him into giving an Engineered Public Confession.
- The Thrombeys telling Marta that they wanted to invite her to Harlan's funeral, but they were "outvoted." The first time it happened, it sounds sincere and apologetic, but it is happening repeatedly, verbatim, is a hint that the family considers Marta an outsider and are completely willing to turn on her.
- In his present-day introductory appearance, Ransom tells the officers to call him Ransom as only the help call him by his first name Hugh. At the blackmail location as a near-overdosed Fran (Harlan's housemaid) gasps "you did this" to Marta, it's later revealed she was actually saying "Hugh did this", further revealing he was the one behind Harlan's death and framing Marta.
- No one in the family knows how old Great-Nana is, treats her like a Living Prop or a burden, and dismisses her when she mistakes people who walk by as Ransom. While it accurately shows how self-absorbed they are, her testimony at the end exonerates Marta and reveals Ransom's role in Harlan's "suicide" after Blanc shows her kindness and respect, showing how much the family messed up by considering her Beneath Notice.
- The mug belonging to Harlan at the very beginning of the movie reads "My House, My Rules, My Coffee." This foreshadows what you need to know about the man. The family is completely dependent upon his wealth which he can gift or rescind to any of them as he sees fit.
- At the end of the movie, Marta is looking down on the family from a balcony...drinking coffee from the same mug.
- Early on, Harlan makes a remark about people "impulsively unraveling the strings on their parachutes." This very habit winds up being his own undoing, with his shooting down of Marta calling the ambulance, which would have saved his life had he listened to her instead of indulging in his flair for the dramatic.
- The interviews between the detectives and Linda, Richard, and Walt. Walt claims he is worth something, Linda will not sell out her younger brother by saying he does not, then Smash Cut to Richard — a Thrombey by marriage to Linda — absolutely selling out Walt. The Thrombey nastiness is on display before Marta ever enters the picture. Walt later makes a veiled threat to Marta that means nothing, Linda treats Marta nicer than most at first but puts even family she disagrees with over her when the will changes, and Richard ends up personifying the entire family's willingness to sell out Marta with the Slayer clause taking pride in family over outsiders.
- After the first act appears to drop the complete picture of the mystery on the audience and goes on to entertain that premise for a while as Marta destroys evidence, the characters enter the house and Ransom is introduced to the cast after having a minimal presence beforehand. Following this, the reading of the will occurs and that character starts to take a role in the story and the narrative dynamic has significantly shifted a second time. Ransom being belatedly established as something of a shakeup during a point where the audience thinks they've gotten all the pieces and are now getting used to the new plotline is no coincidence. Ransom represents most of the pieces the audience doesn't have, as he is the hidden antagonist responsible for Harlan's suicide.
- Right as Marta is about to confess her accidental manslaughter of Harlan to the Thrombeys, Blanc, having just read the toxicology report and learned that Harlan didn't overdose and his blood levels were normal, meaning that Marta didn't kill him, interrupts her, chews out the family, and declares that he's going to (rightfully) have Harlan's death ruled as a suicide. Ransom immediately responds with an incredulous, unhappy-sounding "What?!" Considering that he's been acting as a friend and confidante for Marta and helping her after she confessed to him, he should be relieved to learn that she didn't kill Harlan after all and be happy for her, rather than upset. The real reason he's so dismayed is because he attempted to kill Harlan himself while framing Marta for it and hired Blanc so he would investigate and implicate her for manslaughter, and when he realized she wasn't responsible for his death, tried to destroy all evidence of her innocence so she would never learn this; thus, Blanc stopping her from confessing and declaring the death a suicide ruins Ransom's entire plan.
- Ransom's upset reaction also indicates that he cares a lot more about his family getting the inheritance than he originally let on during the Thrombey family's original disinheritance. At that moment in time, Ransom appears downright ecstatic to see his family thoroughly lose their shit over the realization that they're about to lose everything in their privileged, pampered lives. And he has good reason to as well, since he'd orchestrated a convoluted plan to get both his family and his own wealth back, meaning Ransom can have a good laugh watching his relatives melt down over something that seems temporary at the moment. By contrast, Ransom is nothing short of pissed when Harlan's fortune is denied to his family the second time around, as he's more than aware that his own share of the money is actually in danger of being permanently denied to him.
- The first time Marta tells a lie in front of Blanc, she vomits basically immediately, establishing her complete inability to lie. However, when she lies to him again by claiming that Ransom told her to drive away from the forensic lab, she's able to hold it in long enough to get in the car and vomit in a cup out of sight. Her growing ability to hold her vomit back is crucial to the climax, where she lies about the phone call she just received to say that Fran survived when she actually died. Thinking that she's not dead, Ransom confesses to the poisoning, at which point Marta lets her vomit loose and reveals that he just confessed to murder.
