In the small mining village of Greenall Bridge, Yorkshire, England, a tricolor collie named Lassie is the pride of the community. Owned by coal miner Sam Carraclough, she is considered the finest collie in the region and is famous for her unfailing routine: Every day, just before four o'clock, she trots through the village to meet Sam's 12-year-old son, Joe, at the school gate. The shopkeepers set their clocks by her. For three years, the wealthy Duke of Rudling has tried to buy Lassie, but Sam has always refused, making her a symbol of something money cannot take from the villagers.
When the Clarabelle Pit, the local coal mine where Sam worked for years, closes permanently, the family survives on meager government dole payments. Sam finally accepts the Duke's offer of 15 pounds. One afternoon, Joe arrives at the school gate to find Lassie gone. His mother tells him bluntly that the dog has been sold, and Sam, unable to face his son, leaves the cottage. Joe insists he will never want another dog.
At the Duke's estate, the irascible old man shows his purchase to his 12-year-old granddaughter, Priscilla. Lassie lies listlessly in her kennel, refusing to respond. Hynes, the Duke's kennelman, dismisses her behavior as cottage spoiling. As four o'clock approaches, Lassie's powerful time sense, an internal clock honed by years of routine, drives her to pace her pen.
Lassie escapes three times, each time appearing at the school gate, and each time the Carracloughs must return her. On the second return, Joe delivers a painful farewell through the wire, telling Lassie she is a bad dog and must never come home again. Priscilla, watching unseen, recognizes the anguish behind his words. On the third escape, Joe runs away with Lassie to the moors before Sam brings them both home. Hynes reinforces the pen, and Lassie stops escaping. Sam takes Joe to the moor for a talk about honesty, the one thing a poor man can cling to: Once a dog is sold and the money spent, the deal cannot be undone. He reveals that the Duke has taken Lassie to his Highland estate, hundreds of miles north.
At the Highland estate, Lassie is groomed for dog shows but remains fixated on the south. Priscilla, visiting for the summer, persuades her grandfather to order Hynes to walk Lassie daily. During one walk, Hynes yanks the leash and the noose slips over Lassie's head. Her time sense surges awake, and she breaks into a steady lope heading south. As she races toward the estate's front gate, Priscilla is there, opening it for her grandfather's return. She hears Hynes screaming to close the gate, remembers Joe's farewell, and deliberately swings it wide open. Lassie streaks through, and Priscilla waves good-bye.
So begins a journey of roughly 1,000 miles, guided only by instinct. Men in a Highland village try to catch her for a reward, teaching her to avoid all humans. After four days without food, she overcomes her training never to eat stray scraps and learns to hunt rabbits. Her path brings her to one of Scotland's great lochs, long bodies of water running east to west. She spends over a week working along the shore until the loch narrows to a river. The current batters her against rocks and sweeps her over a cascade. She reaches the far bank with a broken rib, a bruised hind leg, and a festering thorn in her paw. She lies hidden with fever for days before resuming her journey on three functional legs.
Crossing a moonlit field, she is mistaken for a sheep-killing dog by two shepherds. One fires a rifle and creases her flank with a bullet, then releases two farm dogs. Weakened and outnumbered, Lassie fights until both dogs concede. In the industrial Lowlands, she can no longer avoid human contact. Dog catchers capture her in a great Scottish city, but she breaks free from the pound, leaping from a window 20 feet to the ground, and scrambles over a courtyard wall. She crosses the River Tweed into England, swimming the broad current in an effort that nearly drowns her, and collapses on the far bank.
Daniel and Dally Fadden, an elderly couple in a remote cottage, find Lassie in a ditch and nurse her back to health over weeks. As she recovers, her time sense reasserts itself. Every afternoon near four o'clock, she paces and whines to go south. Dally recognizes that Lassie is "on her way" somewhere and stopped at their cottage only as at a wayside inn. After a painful discussion, the old couple open the door and let her go. Lassie looks back once, then strikes out south.
She falls in with Rowlie Palmer, a cheerful traveling potter who drives a horse-drawn caravan with his small trick dog, Toots. When Rowlie turns east at a fork, Lassie refuses to follow until he reverses course southward. One night, robbers attack the campsite. Toots is killed defending Rowlie, and Lassie, who initially fled, charges back and drives the men off. At a crossroads, Rowlie and Lassie part: He must turn east, and she will only go south. A heavy snowstorm catches her on a high moor, and she collapses under the drifts.
In Greenall Bridge, Joe has never stopped looking for Lassie at the school gate. One day he sees a dog dragging itself toward the gate, head and tail down. She drops in her accustomed place and lies still. Joe kneels, confirming she is real, then lifts the emaciated dog and staggers home. Sam and Mrs. Carraclough work over the desperately ill dog through the night. Sam diagnoses pneumonia and says it is hopeless, but Mrs. Carraclough empties a vase of saved pennies, sends Sam for eggs and brandy, and spoons the mixture into Lassie's mouth until she swallows. By morning, Lassie is alive.
The Duke arrives with Priscilla. Joe plants himself at the gate and denies any dog of the Duke's is there. Sam emerges with Lassie, but the dog is unrecognizable: Using his grooming expertise in reverse, Sam has twisted one ear, blotched her coat, and ruined the line of her tail. He asks the Duke whether this dog resembles any of his, knowing that in the world of dog dealing a spoken word is a binding contract. The Duke kneels, lifts a forepaw, and examines the underside, where the pads are crisscrossed with scars from an almost impossible journey. After a long silence, he declares that this dog never belonged to him. He walks away, muttering about 400 miles.
Reminded by Priscilla, the Duke offers Sam a job as kennelman, replacing the dismissed Hynes. Mrs. Carraclough negotiates six pounds a week plus a cottage. The Duke's condition is that the "thick-skulled, screw-lugged, gay-tailed eyesore of an excuse for a collie" (238), with her twisted ear and oddly carried tail, never set foot on his property. Joe agrees, saying Lassie will soon look like herself again. In the car, the Duke tells Priscilla he spent five years trying to get that dog, and now he has her, though he had to hire the man.
Life returns to the way it was. Under Sam's care, Lassie's health is restored; only a slight limp remains. She resumes her daily trot to the school gate, and the shopkeepers once again set their clocks by her. She has a litter of seven puppies. Sam has work, Mrs. Carraclough hums as she serves plentiful meals, and the cottage is warm again. Joe croons to Lassie by the fire, calling her "Lassie Come-home," while his father catches his eye by placing a finger beside his nose in a conspiratorial gesture, the household fully restored.