Warning: MAJOR SPOILERS for Knives Out ahead.
Rian Johnson's twisty murder mystery Knives Out has a lot of surprises, and the ending reveals the true tragedy behind the death of famous author Harlan Thrombey (Christopher Plummer). The film stars Daniel Craig as Benoit Blanc, a private investigator hired to investigate Harlan's apparent suicide following a birthday party at his home. Over the course of the film, Benoit discovers that every member of Harlan's family had a motive to kill him - whether it was covering up a secret affair, or securing a stake in his enormous fortune. But while each of them is guilty of one sin or another, only one of them actually plotted to kill Harlan: his grandson, Hugh Ransom Drysdale (Chris Evans).
Knives Out surprises audiences by showing how Harlan died very early on. He was being given his nighttime medication by his nurse, Marta (Ana de Armas) when the medication was knocked over. Marta picked up the vials but, after giving Harlan the injections, realized that she had switched the vials and accidentally given him a lethal dose of morphine. To make matters worse, the antidote was strangely missing from her medicine bag. Knowing that she would be blamed for his death and her mother could be deported amid the scandal, Harlan gave Marta careful instructions to be seen leaving the house, then return later so that she could go downstairs disguised as Harlan. This would pin his hour of death to a time after Marta had already left.
Before the morphine overdose could kill him, Harlan slit his own throat to make his death look like a suicide rather than an accident. However, the ending of Knives Out reveals that his death was no accident. It was brought about through the actions of Ransom, who had conspired to have Marta accidentally kill his grandfather. Like the rest of his family, Ransom had been cut out of Harlan's will, which instead left everything to Marta. But if Marta appeared to have murdered Harlan, the new will would have been invalidated and the fortune would have been divided up among the Thrombey family - Ransom included.
Ransom unwittingly confesses to his crimes while being recorded at the end of Knives Out, at which point he decides to kill Marta since he's going to prison anyway. Grabbing a knife from the display in his grandfather's drawing room, he attacks Marta and stabs her in the chest... only to realize that he's stabbed her with a trick knife. Ransom is arrested and taken away, Marta inherits Harlan's house and fortune, and the film ends with her looking down on the cast-out Thrombey family from the balcony of her new home. However, the road to this ending is a little complex, so let's break it down in detail.
How Harlan Thrombey Died (& Who Killed Him)
The literal answer to the question of who killed Harlan Thrombey is that he killed himself, cutting his own throat with a knife. The tragedy of his death is that Harlan hadn't actually been given a morphine overdose at all, and there was no need for him to kill himself. Ransom planned to have Marta give Harlan the overdose by switching the labels on the medicine in her bag, and then stealing the antidote so that his grandfather's life could not be saved. However, when the medication was accidentally knocked over the two vials were switched again, so Marta actually gave Harlan the correct and safe doses.
Throughout the film, Marta is riddled with the guilt of believing that she killed Harlan through her carelessness of not checking the labels on the medicine. However, not checking the labels is actually what would have saved his life. Marta knew by the consistency of the liquids which medicine was which, and gave him the correct doses of each on instinct. As Benoit Blanc explains, she got it right despite Ransom's tampering because Marta is a good nurse.
Although Harlan's death was technically at his own hands, Ransom is undoubtedly to blame. Had he not switched the labels on the medicine, Marta would never have believed that she had accidentally given Harlan a morphine overdose, and Harlan would never have killed himself to cover for her. But even if Ransom was only guilty of attempted murder towards Harlan, he seals his fate by committing a number of additional crimes - including outright murder - to try and cover his tracks.
Ransom's Plan and Fran's Murder
Ransom's original plan was fairly simple. On the night of Harlan's death, after storming out over the will change, he returned to the house and climbed up the trellis to avoid being spotted. He switched the labels on the medicine in Marta's bag, and took the antidote for a morphine overdose out of the bag. He then climbed back down the trellis, but was spotted by Harlan's mother, Greatnanna Wanetta (K Callan) - a moment that would later prove crucial to Benoit figuring everything out. Ransom then snuck back into the house during Harlan's funeral, when he knew it would be empty, to switch everything in the medicine bag back and avoid suspicion. He anonymously hired Benoit to investigate Harlan's death, believing that Benoit's detective skills would pin Marta as the killer.
This plan went awry in three ways. The first was that Fran (Edi Patterson), the housekeeper, spotted Ransom tampering with the medicine bag the second time and realized that something was afoot. The second was that Ransom could not possibly have predicted that the medicine vials would be knocked over and that Marta would mix them up all by herself. The third was Harlan's decision to kill himself to ensure that Marta wouldn't get in trouble. After Marta "confessed" to Ransom that she had killed Harlan, Ransom realized that Harlan's blood tests would be perfectly normal, showing no morphine overdose. The death would be ruled a suicide, Marta would receive Harlan's fortune, and Ransom would get nothing.
To ensure that the blood test results couldn't clear Marta's name, Ransom burned down the lab where the tests were held. However, there was another fly in the ointment: Fran. She took the medicine bag from the crime scene and sent Ransom a photocopy of the blood test, revealing that she had her own copy, with the warning, "I KNOW WHAT YOU DID," and instructions to come and meet her. Ransom, as clever as he was nefarious, repurposed the threat - sending the note to Marta so that she would believe she was being threatened with a blood test that proved a morphine overdose. Ransom sent an email to Marta telling her to come to the meeting place after the originally designated time. He met Fran first, gave her a morphine overdose with the intent to kill her, and set Marta up to find her.
This new plan went sideways as well, however. Fran initially survived the overdose, waking up when Marta found her and telling her, "Hugh did this" (it was established earlier in the film that Ransom insists upon "the help" calling him by his first name, Hugh). Marta misheard this as "You did this," still assuming that the blood test showed a morphine overdose and that Fran was accusing her of killing Harlan. However, instead of letting Fran die, Marta called an ambulance to have her taken to the hospital. She then confessed to Benoit, accepting her fate, and showed him Fran's secret stash in the Thrombey mansion, where the copy of the blood test was hidden. Before she could confess to the family, Benoit looked at the blood test and realized that Marta was innocent.
We then get a classic murder mystery accusation scene. Benoit instructs every member of the family except for Ransom to leave the drawing room, and lays out Ransom's whole twisted scheme from start to finish. Marta receives a call from the hospital, and triumphantly tells Ransom that Fran has survived and will be able to testify against him. Believing he's doomed anyway, Ransom admits his crimes. Marta reveals that she was recording his confession, and then promptly vomits - an involuntary response she has to telling lies. Fran had actually died of the overdose, and Marta tricked Ransom into confessing when he didn't have to.
The REAL Meaning of Knives Out's Ending
Despite the grim subject matter and tragic nature of Harlan's death, Knives Out's ending ultimately has an optimistic outlook. Marta escapes being framed for Harlan's murder and going to prison because, ultimately, she's a good person. She initially tried to cover up how Harlan died less to protect herself, and more to protect her family and carry out Harlan's final instructions. However, she was wracked with guilt over the cover-up and decided it had gone too far once someone got hurt. Had Marta let Fran die and chosen not to confess to Benoit, Ransom would have gotten away with everything and Benoit would have never found the blood test that cleared her of all guilt. Marta's inherent goodness is symbolized by the fact that she can't even tell a lie without vomiting.
Marta's humility is strongly contrasted with the spoiled, self-involved, and entitled Thrombey family. Knives Out takes aim at the idea of privileged white people considering themselves to be "self-made" despite relying on inherited wealth and family connections for their success. Walt (Michael Shannon) runs the family publishing company, but was given the job by his father. Harlan's daughter-in-law Joni (Toni Collette) has been sponging off him for years and even double-dipping into the allowance for Meg's (Katherine Langford) tuition. Meg is outwardly progressive and feminist and pretends to be a friend to Marta, but with just a little nudge is ready to manipulate Marta into surrendering Harlan's fortune. Linda (Jamie Lee Curtis) runs her own business, but got the start-up money from Harlan. Ironically, Ransom is the only member of the family who actually works to earn his share of the fortune... by putting together an elaborate murder plot.
When the Thrombeys find out that Harlan has left his entire fortune to Marta, they are outraged, feeling that something has been stolen from them. But in fact, Harlan's wealth was never theirs to begin with, nor did they actually earn any of the money he gave them over the years. Harlan chose to leave his fortune to Marta because she was kind to him without having an agenda, and had worked hard her whole life for very little reward. In pitting Marta against the Thrombeys, Knives Out challenges the idea of inherited wealth and lays bare the entitlement and poor character of those who receive it.
Ransom lays his plans with the belief that everyone - Marta included - is as self-serving and corrupt as he is. But all Marta has to do to scupper those plans is to be what she already is: a good nurse, and a good person.