A boy's evil twin leads him on the path to murder.

In 1935 in the rural Connecticut town of Pequot Landing, twelve-year-old Niles Perry is admiring a large ring on his finger when his mischievous twin brother Holland goads him into sneaking into the home of elderly neighbor Mrs. Rowe. When Holland's attempt to steal some of the old woman's preserves results in a broken jar, Holland escapes, leaving the hapless Niles to take the blame. Upon returning to the Perry farm later, Holland races into the barn while Niles evades queries from his nosy cousin Russell and greets Russell's parents, Aunt Vee and Uncle George, who live with the twins, their widowed mother Alexandra and older sister Torrie, her husband Rider Gannon and Alexandra's Russian-born mother, Ada. Joining Torrie and Rider in the house, Niles happily asks about his sister's pregnancy and declares his conviction that the baby will be a girl. Niles then goes in search of Holland who is sulking in the apple cellar. As Niles again admires his ring, decorated with the family emblem of a peregrine falcon, Holland warns him to be more cautious with it. Handed down from the Perrys' grandfather, the ring went to Holland upon the death of the twins' father a year earlier and Holland later presented it to Niles after their birthday. Just as Niles places the ring inside a Prince Albert tobacco can in which he carries several cherished treasures, Russell appears, demanding to know why Niles is in the off-limits cellar. Niles attempts to mollify his cousin, but Russell declares he will inform the adults, then darts away. Niles then recalls that the cellar has been forbidden since the previous autumn when the cellar door crashed down upon his father and killed him. Up in the barn, Holland, angered by Russell's taunts, kills his cousin's caged pet rat. Distraught, Niles buries the creature in the garden, then spotting his mother on the balcony, rushes to visit her. Emotionally fragile since her husband's untimely death, Alexandra has remained secluded for many months. Niles chats brightly with Alexandra about the books he brings her from the library, but she is startled when the Prince Albert can tumbles from underneath Niles's shirt and several objects fall out. A little later, after Holland goes fishing, Ada joins Niles in the garden and when she inquires why he never plays with Russell, he admits to disliking his cousin. Niles then asks Ada if they can play the game she has taught him, in which he imagines himself becoming an object or animal. Ada selects a crow, and, at her urging, Niles concentrates and imagines himself soaring in the sky as the crow takes flight. As the crow flies over the Perry farm, it circles the barn, where inside Russell repeatedly hurls himself from the loft into a large pile of hay below. Niles abruptly ends his imaginative flight and as he and Ada start back to the house, they hear a terrible shriek as Russell impales himself on a pitchfork propped up in the hay. After Russell's funeral, Niles comes upon farmhand Leno Angelini, who is distraught that his carelessness caused Russell's demise, but Niles assures him it was an accident. Later, alone in the twins' bedroom, Niles opens the Prince Albert can and, unwrapping dark blue tissue paper, stares at a gray, severed finger. A few days later at the local carnival, Holland and Niles sneak into the tent housing the freak show and later, despite Holland's ridicule, Niles watches the performance of Chinese magician Chan-yu and his vanishing box. Niles concentrates on the magician's lacquered cabinet in which his assistant binds and locks him and realizes there is a trap door under the box that allows the magician to escape. That evening Niles relates to Ada that he was able to perform "the game" at the carnival to figure out the magician's trick, but his grandmother reminds him that the game is only imaginary and that he must live real life. Ada then tells Niles that he must apologize to Mrs. Rowe and Niles assures her that he will tell Holland. The next day, Holland, dressed in a magician's cape and top hat, visits Mrs. Rowe to apologize and present her with a jar of preserves. The elderly woman invites the boy inside where he offers to demonstrate a magic trick for her. Doffing his hat, Holland pulls out a white rat that sends Mrs. Rowe into hysterics. That afternoon, Niles joins Ada at the local church, where he asks her why people die. Ada explains that death is part of life's cycle and relates that as a child she was afraid of death until her grandfather told her to find an angel that would provide her comfort and vanquish her fears. Upon returning home, Niles is delighted to see Alexandra outside and confides that he wants to put on a magic show. Later, after joining Holland by the pond, Niles tells him about the comforting angel Ada described to him, but Holland mocks him. The twins then gather cattails with which to decorate the apple cellar floor, but are angered when, returning to the barn, they discover the back entrance to the cellar padlocked. Outside, Niles accompanies Ada to pay a call on Mrs. Rowe, but when they reach the house and receive no answer to the doorbell, Ada peers in the window and sees Mrs. Rowe's dead body. Niles hurries back to the Perry house to have someone call the constable, then wanders upstairs where he surprises Alexandra in the twins' bedroom. Scurrying away clutching the ring and blue tissue, Alexandra locks herself in her room. Holland joins Niles, cursing viciously over their mother's discovery of the Prince Albert can and demands that Niles recover the ring and the tissue. That night, Niles sees Alexandra in the garden and when she collapses weeping against the sealed-up well, he rushes to her aid. After leading her back to the balcony, Niles pries open his mother's hand and takes the ring. Alexandra asks him how he got the ring as it was supposed to be buried, but Niles insists that Holland gave him the ring in the parlor. When Alexandra then holds up the severed finger and asks if Holland gave him that as well, Holland darts out of the shadows, insisting the blue tissue is his. In the ensuing struggle, Alexandra falls down the stairs. As a result of her fall, Alexandra, now paralyzed and unable to speak, is confined to a wheelchair. Holland remains cavalier about his mother's condition, while Niles is deeply troubled. A few days later, Ada finds Niles at the church, gazing in rapture at the stained glass image of an angel. Ada tells Niles that she found Holland's harmonica at Mrs. Rowe's and mentions that the old woman apparently died of fright. When Niles admits that Holland has behaved very badly, Ada angrily demands that he accompany her outside where she drags the protesting boy to a gravestone and insists that he read the marker inscribed with Holland's name that indicates the date that he died was on their last birthday. Remembering that Holland's attempt to hang the family cat in the empty well resulted in his falling in to his death, Niles faints. That night, Ada sits with a feverish Niles and pleads for his forgiveness for having encouraged him into flights of imagination as she could not bear to see him so lonely after Holland's death. Ada then insists that Niles never play "the game" again and he reluctantly agrees. After Ada retires, Holland creeps out of the shadows and directs Niles to the parlor where Niles remembers Holland lying in his casket instructing him to take the ring from his finger. Unable to pull the ring from his brother's swollen hand, Niles follows Holland's suggestion to cut off the finger with rose shears. When Niles reveals that he can no longer play "the game," Holland warns him that if he does not, he will truly be alone. A few days later, Torrie and Rider return from the hospital with their new baby girl, while Niles reads to the silent Alexandra. Later in the barn, preparing for the magic show, Niles hears noises and finds Angelini drunkenly breaking into a large barrel of wine. Several nights later, Torrie and Rider spend their first evening away from the baby, whom they leave under Aunt Vee's and Ada's care. Later that night, a violent thunderstorm breaks out, wakening Niles who rushes to the nursery to discover the baby missing. The police are summoned and amidst the uproar, Ada notices Niles heading to the barn and follows. There she overhears him calling to Holland, demanding to know what he has done with the baby. Horrified, Ada asks him what he means and Niles confesses that Holland has been responsible for all the terrible events, from setting the pitchfork up to kill Russell, to frightening Mrs. Rowe, to pushing Alexandra down the stairs and even killing their father to get the ring. When Niles resumes calling Holland, Ada grabs him and demands that he acknowledge that Holland is dead. Rejecting his grandmother, Niles heads for the apple cellar while calling for his brother. Ada returns to the main house where the baby's body is discovered floating in the full wine barrel. Stricken, Ada returns to the barn and hearing Niles in the apple cellar, pours kerosene across the floor. As Niles listens, confused, Holland whispers taunts in his ear, asking him if he knows who he really is. Seeing a light in the doorway above him, Niles looks up, imagining the face of the stained glass angel, but it is Ada, holding a burning kerosene lamp as she plunges down the stairs onto the kerosene-soaked floor, igniting a conflagration. A few days later, the charred barn is razed and the workers fail to notice the remains of the back door, its lock cut. In the house, Niles peers out the window watching, until his aunt calls him to lunch.