The film opens with a little girl jumping rope and counting stars to "a hundred".The film's plot centres on three married women — a grandmother, her daughter, and her niece — each named Cissie Colpitts. As the story progresses, each woman successively drowns her husband. The three Cissie Colpittses are played by Joan Plowright, Juliet Stevenson and Joely Richardson, while Bernard Hill plays the coroner, Madgett, who is cajoled into covering up the three crimes. The structure, with similar stories repeated three times, is reminiscent of a fairy tale, most specifically 'The Billy Goats Gruff ', because Madgett is constantly promised greater rewards as he tries his luck with each of the Cissies in turn. The link to folklore is further established by Madgett's son Smut, who recites the rules of various unusual games played by the characters as if they were ancient traditions. Many of these games are invented for the film, including: In Drowning by Numbers, number-counting, the rules of games and the repetitions of the plot are all devices which emphasise structure. Through the course of the film each number from 1 to 100 appears, the large majority in sequence, often seen in the background, sometimes printed on cattle, sometimes spoken by the characters. The repetitive, obsessive motif of the film echoes that of the soundtrack by Michael Nyman. The film is set and was shot in and around Southwold, Suffolk, England, with key landmarks such as the Victorian water tower, Southwold Lighthouse, and the estuary of the River Blyth clearly identifiable.

25 years old Sibel lives with her father and sister in a remote village in the mountains of Turkey's Black Sea region. She is mute and communicates by using the ancient whistled language of their region. Despised by her fellow villagers, she relentlessly hunts down a wolf sneaking in the neighboring forest, sparking off fears and fantasies among the villagers. There she crosses path with an injured and vulnerable fugitive, who is the first one to see her differently.

To stop a solar flare from destroying the Earth, Steve Kelso is tasked to drop an artificially intelligent bomb on the Sun from the spaceship Helios. Arnold Teague, who believes the danger to be overstated, attempts to sabotage the mission so he can profit from the panic. Teague's agents on Earth clash with Kelso's father, Admiral "Skeet" Kelso, and his son, Mike.

A Jewish man in a 19th-century Eastern European shtetl tells his wife that he was helped on his way home by Reb Groshkover, whom he has invited in for soup. She says Groshkover is dead and the man he invited must be a dybbuk. Groshkover arrives and laughs off the accusation, but she plunges an ice pick into his chest. Bleeding, he exits their home into the snowy night. In 1967, Larry Gopnik is a professor of physics living in St. Louis Park, Minnesota. His wife, Judith, tells him that she needs a get so she can marry widower Sy Ableman, with whom she has fallen in love. Meanwhile, their son Danny owes twenty dollars to an intimidating Hebrew school classmate for marijuana. He has the money, but it is hidden in a transistor radio that his teacher confiscated. Their daughter, Sarah, is constantly washing her hair, going out, and avoiding school. Larry's brother, Arthur, is homeless and sleeps on the couch, spending his free time filling a notebook with what he calls the "Mentaculus", a "probability map of the universe". Clive Park, a South Korean student worried about losing his scholarship, meets with Larry in his office to argue that he should not fail the class. After he leaves, Larry finds an envelope stuffed with cash. When Larry attempts to return it, Clive's father threatens to sue Larry either for defamation if Larry accuses Clive of bribery, or for keeping the money if he does not give him a passing grade. Larry faces an impending vote on his application for tenure, and his department head informs him that anonymous letters have urged the committee to deny him. At the insistence of Judith and Sy, Larry and Arthur move into a nearby motel. Judith empties the couple's bank accounts, leaving Larry penniless; his attorney advises him to open a private account. Larry turns to his Jewish faith for consolation. He consults a junior rabbi, Scott, who advises Larry to change his "perspective". Larry and Sy are involved in separate, simultaneous car crashes. Larry is unharmed, but Sy dies. Larry consults a second rabbi, Nachtner, for solace, who recounts an anecdote about an orthodontist who finds Hebrew inscriptions on a non-Jewish patient's teeth. Larry also tries to contact Marshak, the synagogue's senior rabbi, who is not available. At Judith's insistence, Larry pays for Sy's funeral. At the funeral, Sy is eulogized as "a serious man". Larry calls on his neighbor, Vivienne Samsky, whom he has seen sunbathing naked. She introduces him to marijuana. He later dreams that he is having sex with her, but this turns into a nightmare. Larry learns that Arthur faces charges of illegal gambling, solicitation, and sodomy. Arthur is despondent about the charges against him, and Larry consoles him. Larry then has another nightmare in which he gives Arthur the money Clive left him and drives him to cross into Canada by boat, only for his neighbors to shoot Arthur in the neck. Larry is proud and moved by Danny's bar mitzvah, unaware that his son is under the influence of marijuana. During the service, Judith apologizes to Larry for all the recent trouble and tells him that Sy respected him so much that he even wrote letters to the tenure committee. Danny meets with Marshak, a brief encounter in which Marshak only quotes Jefferson Airplane 's " Somebody to Love ", names some members of the band, returns the radio, and tells Danny to "be a good boy". Larry's department head compliments him on Danny's bar mitzvah and hints that he will receive tenure. The mail brings a $3,000 bill from Arthur's lawyer. Larry decides to change Clive's grade from F to C−; immediately after he does so, his doctor calls, asking to see him immediately about the results of a chest X-ray. Meanwhile, Danny's teacher struggles to open the emergency shelter as a massive tornado closes in on the school.

Thomas de Frémont, a child prodigy obsessed with tinkering and action films, lives in a secluded and high-tech castle with his widowed mother, Julie, his diabetic and partially blind grandfather, Papy, and his pet dog, J.R. On Christmas Eve, Thomas uses the Minitel to try and communicate with Santa Claus and unknowingly makes contact with a derelict who is using a public Minitel terminal. The deranged man claims to be Santa and attempts to get Thomas to divulge his address; before their connection is severed, the vagrant learns Thomas's mother manages a nearby Printemps. While Thomas sets up a security system to record or capture Santa, the vagabond gets a job as a Santa at the Printemps but is fired from it after Julie witnesses him slap a child who accused him of not being the real Santa. The vagrant subsequently steals a Santa suit, paints his hair and beard white, and hitches a ride to Julie's home in the back of a delivery van, the driver of which he kills upon reaching the de Frémont residence. The man then murders Julie's groundskeeper and her chef, breaks into her home through the chimney, and stabs J.R. to death in front of Thomas, who is convinced the intruder is an enraged Santa. What follows is a game of cat and mouse as Thomas uses his security system and booby traps, as well as an arsenal of makeshift weaponry, to defend his enfeebled grandfather and combat the trespasser, who has cut the telephone lines and trashed the only car; the man at one point catches Thomas but then lets him go while declaring, "I win. You lose. Now I hide and you seek. Okay?" Julie, concerned over her calls home not getting through, phones the police, who send an officer to the castle to check on Thomas and Papy. The vagrant murders the policeman and recaptures Thomas, but the boy is saved when his grandfather shoots his assailant with the dead officer's gun, with Julie arriving home seconds later to find a stunned Thomas standing over the killer's body, stammering, "It's my fault, Mom. I wanted to see Santa Claus."

In 1961 London, Jenny Mellor is a bright and attractive 16-year-old schoolgirl who aspires to attend the University of Oxford. Her studies are controlled by her strict father, Jack. After youth orchestra rehearsals, Jenny waits at a bus stop on the street in heavy rain when David Goldman, an older man, stops his Bristol 405 and tells her that he is a music lover and is worried about her cello getting wet. He persuades Jenny to put her cello in his car while she walks alongside. As the rain becomes heavier, Jenny asks David if she can sit inside the car. The two talk about music and, before being dropped off, Jenny confides that she is looking forward to attending university and being able to live a life of culture, doing things such as going to art galleries and watching French films. The following week, David has flowers delivered to Jenny's house, wishing her luck at her youth orchestra's concert. Later, she sees him in town and approaches him. David asks Jenny if she is free to go and see a concert and have supper with him and his friends. She happily agrees and thanks him. On the night of the concert, Jack disapproves of Jenny going, but when David comes by to pick up Jenny, he easily charms Jack into letting him take Jenny and bring her home later than her normal curfew. Arriving at the concert, Jenny meets David's friends, Danny and Helen. Afterwards, they go to dinner at a fancy restaurant with live music much to Jenny's liking. Finding she is also interested in art, they invite Jenny to an art auction. David picks up Jenny at school and they go to the auction, winning a bid for a painting by Edward Burne-Jones and going to Danny's place afterwards. They talk about Oxford and all agree to go and visit together the following weekend. Jenny hears a commotion late one night and sees David drinking with her parents. He then uses the opportunity to ask them if he can take Jenny to Oxford, saying that he used to study there and would like to visit his old teacher, Clive Lewis, the author of The Chronicles of Narnia. Her parents are reluctant at first, but agree, seeing it as a good opportunity. At Oxford, Jenny discovers that David makes his money through a variety of shady practices, and although initially shocked succumbs to David's persuasive talk. Back outside her home, Jenny and David have their first kiss. Jenny then shows a signed copy of The Lion, the Witch and the Wardrobe to her parents (in fact, she had seen David sign it, and they had never met Lewis). Impressed by David's apparent connections and charisma, Jack and Marjorie approve of their romantic relationship. On the night of Jenny's 17th birthday, David arrives with presents and tells her parents that he intends to take them all to Paris as a special birthday gift. Her father demurs, but following a conversation with David agrees to Jenny going with him alone. In Paris, the two go sight-seeing, take photos, and go dancing, and Jenny loses her virginity to David. Back in London, Jenny gives her favourite teacher, Miss Stubbs, Chanel perfume as a gift from her trip, but Miss Stubbs refuses the gift, telling Jenny that she knows where it came from and is both concerned and disapproving of her relationship with David. They argue and have a falling-out. Later that night, David proposes marriage. After talking with her parents, Jenny accepts the proposal, but the news causes an argument with her headmistress, and she decides to drop out of school and not pursue a place at university. While getting petrol on their way to a celebration dinner with her parents, Jenny looks in the car's glove compartment for a cigarette and discovers, through letters, that David is already married. Shocked, Jenny tells David to take her and her parents back home. Jenny tearfully argues with David, telling him she gave up her education to be with him. David says he will get a divorce and agrees that he will tell her parents the truth with her, but after she goes inside her house, he drives off and is never seen again. Jenny despairs, and goes to see Danny and Helen, blaming them for not telling her the truth early on. She also blames her parents for encouraging her to throw her life away with an older man. Jenny goes to see David's wife, who tells her that David is a serial adulterer, and has a son. Later that night, Jack apologizes to Jenny, admitting that he messed up and that he believed David could give her the life she wanted. Jack points out that although David wasn't who he said he was, Jenny had also deceived her parents about David's nature by playing along with some of David's lies to her parents. When Jenny is then refused re-admission to her old school to repeat her last year and take her exams, she goes to Miss Stubbs, apologising and asking for her help. Miss Stubbs eagerly agrees, and Jenny resumes her studies and is accepted at Oxford the following year. In a closing voiceover, Jenny shares a story about dating boys her age and starting over with fresh eyes, despite her experience with David.