One night, Dicey 's Momma wakes her four children up in the middle of the night, has them pack clothes and food into paper bags, and begins driving with them from their ramshackle house on the dunes in Provincetown, Massachusetts, to her Aunt Cilla's house in Bridgeport, Connecticut. They stop inexplicably at a mall in Rhode Island, and Momma tells the children to mind Dicey before striding off into the mall. Dicey, who is thirteen years old, senses something is wrong. Her ten-year-old brother, James, entertains the two youngest siblings, the spunky six-year-old Sammy and the docile, eight-year-old Maybeth with the story of Hansel and Gretel. Dicey muses to herself, enumerating all the strange occurrences causing her to suspect something is wrong: first, they have never driven so far and never met Aunt Cilla before. Second, problems have been raining down on Momma: she lost her checker's job, and she is worried about Maybeth, who had already been held back twice. Third, Momma has become even more absent-minded than usual lately. Dicey senses what turns out to be true: Momma has wandered off and is not going to come back.
The children eat in the mall and plan to sleep in the car. Before they sleep, however, Dicey calls the bus station and finds that, since they have spent money on supper, they can no longer afford bus tickets to Bridgeport: they have only seven dollars, two dollars short of the fare they need. While she is using the payphone, an overweight security guard approaches her suspiciously. He thinks she is a boy and begins to interrogate her about windows that have been broken recently in the mall. Dicey lies to him smoothly about her identity, fearing that if he finds the truth, the children will be taken into custody and, eventually, broken up and sent to foster homes. When the security guard becomes more aggressive, Dicey runs swiftly and hides from him, returning to the car only after he has left.
James wakes with words that become his mantra for the next several days: "It's still true." Dicey informs the other children of her plan: they will walk to Bridgeport. Dicey, having consulted the map, estimates it will take them two days. Sammy, however, stubbornly refuses to leave, insisting that Momma could not leave him and will surely come back for him. Dicey reasons with him, and contends that Momma has forgotten where she left them, but will meet them in Bridgeport. She insists to him that it is crucial they stay together. With a simple look and gentle urging, Maybeth finally convinces Sammy to come. After they have left the car, the children watch as a police car draws up to it and an officer gets out and begins to write in his notebook. The children begin to walk along the noisy and heavily trafficked Route 1. They walk all morning, resting at a McDonalds, where Dicey buys sodas for the children, and later lunching on fruit, stale doughnuts, and milk from a supermarket.
The children try to lift their spirits with songs and with a fantasy that they are a small army, marching forward together. During their walk, James and Dicey discuss their home: James mentions that other children thought their home should be demolished, but Dicey defends it, asserting that its location right on the water more than made up for its shortcomings. The children are chagrined and frightened when, during one of their breaks, an angry woman brandishing a broom chases them off. Sammy refuses to walk, again threatening to stay behind, and Dicey, near panic, agrees to carry him on her back. Finally, Dicey buys food for supper and they leave Route 1, soon finding an abandoned house in a copse of trees. They fall asleep immediately and wake in the early evening. Dicey again consults the map, and, finding that they have only gone six miles, quickly reassesses her predictions: now she estimates the trip will take them two weeks. Sammy argues petulantly with Dicey over supper, and though the children sing again into the firelight, Dicey cannot help thinking wistfully of Sammy's infancy, when he had been exuberant, uninhibited, and full of laughter. The children sleep on the porch of the house, tucked away from the gaze of the world.
From the outset of the book, thirteen-year old Dicey struggles to fill an adult role, which Momma has bequeathed to her. Dicey understands that, by starting this strange journey with its strange destination, her mother has tacitly told her to do what she herself cannot do: take the other children to Bridgeport. Moreover, she has, by telling the children to mind her, given Dicey the authority of a mother, and Dicey, desperate to keep her family together and suspicious of the outside world, calls upon this authority throughout the children's arduous journey. Dicey becomes her sibling's mother because, whether she likes it or not, and whether she is particularly good at it, the situation demands that she must become their mother. Besides inheriting this adult responsibility, Dicey maintains the liabilities of being a child. Not only must she be her sibling's sole caretaker and provider, she must do so without any of the resources and capabilities of an adult. Moreover, she must undertake their challenging journey without asking the help of other adults and without attracting their attention, for adult attention will only bring them trouble.
To keep away the dark and threatening possibility, voiced only once, of being separated and put into foster home, Dicey focuses on the need to hold on. First and foremost, she holds on to her family: she emphasizes to Sammy that they must stay together, and she insists they sleep close together. Almost without knowing why, she wants to keep the family out of the notice of the adult world, and to keep them together. Secondly, Dicey tries to assert control by quickly and decisively planning their journey. She calculates the number of days they will walk, counting the miles, and trying to control of the course of their lives. Dicey tries to hold on to money by buying food as cheaply as possibly and keeping meticulous track of the money they have spent. Dicey's careful accounting of the days of walking and the resources they have is only a substitute for real control: she is only able to understand exactly where they are, exactly how much money they have, and how many days of walking they have left. She cannot understand how they can make the money they have last the number of days they must walk, much less understand how they can keep walking when one day has exhausted them so thoroughly. Dicey buries her doubts by focusing on her immediate goals: walking as far as they can, spending as little as possible, and staying together.
Part of Dicey's almost unnamable fears stem from the adult world. The primary and most immediate threat is that of separation: for reasons not fully explained, Dicey assumes that going to the authorities will ultimately result in the dissolution of the family unit. This assumption is clearly based on Dicey's growing but unnamed certainty that Momma is no longer fit to take care of them, or has abandoned them willfully. Momma represents the first and foremost example of an adult who has let them down: while Sammy refuses to accept the possibility that Momma has left them, James increasingly believes that she has failed them in some way, which he hints at with his disparaging comments about their house. Moreover, from the beginning of their journey, hostile adults surround them: first the witch in the story of Hansel and Gretel, which James narrates to Maybeth and Sammy soon after Momma leaves; then the security guard; and the next day the policeman inspecting their car and the belligerent woman waving the broom. The children's greatest fear is that they will be turned over to a strange adult, who almost certainly does not have their best interests in mind. They hold desperately to the hope that Aunt Cilla will be able to fulfill the role Momma once filled and keep them safe from the threatening outside adult world.