Outside a Korean rural town, married couple Jae-Gu and Sun-Young run a roadside garage,
but unfortunately they don't have many clients, in fact most drivers don't even notice their little
shop. This means they're barely making enough to survive, and this makes Sun-Young's relationship
with her family tenser than it already was. They never approved of Jae-Gu because of his low status
and his sterile seed, and now that Sun-Young has to help the household by making dolls just for a
few cents only makes them hate him more. To make matters worse, an important construction company
is working nearby, meaning they take over the roads with their trucks and block the garage
from potential clients. One morning, a frustrated Jae-Gu goes to the construction site to try to ask
the manager and his wife Ye-Ri for compensation, but after he accidentally bumps into their child,
he's seen as a crazy person and taken away by security. Jae-Gu ends up in the police station,
where they are used to seeing him brought over for all the scenes he's always causing,
and an officer reminds Jae-Gu this is what he gets for not wanting to join the local
shop association because their members did get compensation. Another cop informs him of some
rumors regarding his father-in-law: he's the owner of the shop Jae-Gu's renting for his business,
and the old man is thinking of selling. On his way home, Jae-Gu sees a man with a broken truck
and learns he's about to scrap it, so he points out that isn't necessary yet: just by changing
the valve it can run for a few more years. When Jae-Gu arrives at his house, he asks Sun-young if
the rumors are true, and she confesses her dad has been frustrated because they haven't been
paying taxes. Jae-Gu gets angry because she's been keeping this from him, and before the argument can
escalate, he leaves the house to clear his head. The idea is to get some beer and cigarettes at
the local grocery store, but he can't afford both, thus he ends up only buying cigarettes, having to
change to the cheapest brand as well. However the old lady in charge remembers Jae-Gu from the time
he took her granddaughter to school and as thanks, she gifts him a beer can anyway. While enjoying
his beer and cigarettes outside the store, Jae-Gu is approached by the head of the shop association
Mr. Mun and his men, who beat Jae-Gu up for the advice he had given to the man with the truck.
It turns out Mr. Mun had almost put his hands on those scraps for cheap and Jae-Gu got in the way
of his business. Later when Mr. Mun is telling his friends what happened over dinner, the group
starts gossiping about Sun-Young's horrible marriage choice, and Mr. Mun leaves in a huff
because he still harbors feelings for her. A few days later, Sun-Young goes to a family gathering
alone and is immediately attacked by her relatives for her life choices. Jae-Gu shows up as well,
having borrowed some nice clothes and even saved some money for a cake to impress everyone, but
when he arrives and overhears everyone insulting him, he decides to leave without even announcing
himself. On his way home, he accidentally drops the cake, and he's so frustrated by the whole
situation that he kicks it with anger instead of picking it up for dinner. At that moment,
Jae-Gu notices a car stopping in the middle of the road because of a flat tire, so of course
he immediately offers his services to change it as he explains the construction trucks that pass
by drop all kinds of scraps. Since it's late at night and they're in the middle of nowhere,
Jae-Gu takes the chance to charge extra for the job, knowing the client has no choice. Afterward,
he goes back to the road to check on anything else that may've fallen from the trucks just
in time to see Sun-Young arrive in a relative's car. The driver doesn't even say hi to Jae-Gu,
and when he complains, it triggers an argument with Sun-Young, who is tired of being caught
between her family and her husband. To calm her down, Jae-Gu shows her he made some money
tonight. When they go to bed, Jae-Gu can't sleep because he's still bothered by today's events,
so he decides it's time to do something and returns to the road to scatter a bunch of scraps
all over the place. The plan pays off and the next morning they have a new client with a flat tire,
but this time Jae-Gu charges a more reasonable price. Hours pass and Jae-Gu worries because
only one more client came by, so he goes to check on the scraps and finds them all
gone. It turns out the construction trucks have been pushing the scraps away when they drive by,
and because of the size and weight of their tires, they didn't get flat. Not ready to give up yet,
Jae-Gu stays up late making new more pointy scraps that he scatters on the road again,
and this time he's discovered by Sun-Young, who disapproves of the idea. These scraps could cause
an accident or get Jae-Gu arrested, but he changes his mind when he points out all the people that
drive through this road are rich tourists that are always getting out of trouble through bribes,
meaning there's nothing wrong with scamming them. As a final touch on his argument,
Jae-Gu also mentions wanting to save money to buy the shop from his father-in-law. Sun-Young's
initial skepticism slowly melts as days pass and she sees the money this idea brings in, finally
allowing them to buy better food. One morning, Ye-Ri's car is the latest victim of a flat tire,
and while Jae-Gu does his job, Sun-Young offers her a drink and conversation to keep her happy and
paying. However Ye-Ri is incredibly condescending towards them because of their social status, and
when she hears Sun-Young only makes five cents for every ten dolls, she buys one for ten bucks out of
pity. Feeling insulted at the fact she's being treated like a charity case, Sun-Young finally
goes all out and helps Jae-Gu make an argument for why he needs to charge Ye-Ri so much money just
for a tire replacement. From then on, she's more supportive of her husband's plan, bringing him
drinks while he makes scraps and even admitting she would love to have money to dress like Ye-Ri.
Late at night, Sun-Young also begins going with Jae-Gu to the road to hold the flashlight while
he drops the scraps and offers some ideas to make the plan better, like sticking nails to the ground
instead of having to come back every night to replace the scraps. One evening, they're found
by a police officer that wonders what they're doing on the road at this hour, but they manage
to quickly get him off their backs by pointing out he's using the police car for personal matters,
judging by the fact he isn't wearing his uniform and there's a girl with him. The next morning,
the couple doesn't have any clients because they're laying low for a few days after their
encounter with the police. But since Sun-Young's received her payment for the dolls, they decide
to treat themselves with it. Jae-Gu goes to the grocery store for beer and to clear his debt,
taking the chance to give the kid a ride on his scooter to celebrate; and Sun-Young does her hair
in the salon for the first time in years. The fact the couple is doing better financially now
soon reaches Mr. Mun's ears, who begins getting suspicious. When night falls, Jae-Gu and Sun-Young
return to the road with a drill and stick their first nail in the pavement. The new plan works,
and soon Jae-Gu tells Sun-Young she can buy as many dresses as she wants, but he won't
be spending much because he wants to concentrate on buying the shop. Meanwhile Ye-Ri discovers her
kid has been kidnapped. When the police ask her about anyone that may have a grudge against her,
she comes across the doll she bought from Sun-Young and accuses the couple of being
scammers. The police chief doesn't think he has enough evidence to arrest them, but things take
a quick turn when one of the officers shares the fact he saw the couple behaving suspiciously on
the road the other night. In just a few hours, the cops find Jae-Gu and arrest him but not Sun-Young
since they've heard about him making a scene on the construction site and bumping against the
child, making him the prime suspect. While Jae-Gu is interrogated at the station, the police search
the shop, and Sun-Young's dad has to be there as the owner. Instead of being helpful and supportive
of his daughter though, he keeps insulting Jae-Gu and telling Sun-Young that she's reaping what
she's sown. At the end of the day, there's no evidence to be found anywhere and Jae-Gu
is released without charges. The police chief drives him home as an apology but while at first
he shows an understanding of his situation, soon he's telling Jae-Gu to stand up for himself and
to stop bringing his men trouble. The following morning, Jae-Gu gets his tools ready to go back to
the road since they've been losing money while he was away. Sun-Young worries about her husband and
the possibility of being found out, but she can't convince him to take a break. In the meantime,
Mr. Mun is still convinced that Jae-Gu is hiding something and since the police can't do anything
without proof, he agrees with his brother the cop to take turns keeping an eye on the garage couple.
The next time Sun-Young goes to the road to stick a nail in it, Mr. Mun sees her and finds the nail
after she's gone, so now he has to think of a way to use this information in his favor. Now that
the nails are out again, business picks up once more and the garage couple can afford to eat out,
so they don't hesitate to treat themselves. One afternoon, an elderly couple gets a flat tire on
their way to the hospital and asks Jae-Gu for a discount, but he still charges them the full
price. That same day, Sun-Young goes to the grocery store and is approached by Mr. Mun,
who confesses he knows about the nails and asks Sun-Young to come to see him in private if she
wants him to keep the secret. When night falls, neither of them can't sleep: Jae-Gu feels guilty
about overcharging the elderly couple because now he keeps thinking about his own dead parents,
and Sun-Young is worried about what Mr. Mun may do. Pretending to be asking a rhetorical question,
Sun-Young wonders what they should do if someone ever found out about their scam, and Jae-Gu
replies he would quit before that person went to the police. The following day, Sun-Young thinks
thoroughly about how much this plan has improved their lives and takes the hardest decision in her
life: she goes to see Mr. Mun and accepts to get busy with him in the backseat of his car
to buy his silence. Afterward, Mr. Mun tells his brother to drop the surveillance on the garage
couple. Paying for Mr. Mun's blackmail leaves Sun-Young feeling incredibly dirty, so when she
comes across some old friends that invite her to come shopping with them, she accepts in order to
take her mind off things. By the time she returns home, it's incredibly late but she's looking like
a whole new person with her new hairdo and dozens of cute dresses. Jae-Gu complains about the lack
of homemade dinner, but Sun-Young ignores him and takes a shower using a dangerous solvent
because there isn't enough money in the world to make her feel clean again. It isn't until Jae-Gu
goes to sleep that Sun-Young allows herself to cry her heart out. A few days later, a car crashes in
the rice paddy near the garage. Knowing the police will be there soon, Jae-Gu rushes to the road to
take out the nails and notices a man coming out of the car. As soon as this man sees he isn't alone,
he runs away as if he was guilty of something, so Jae-Gu checks the car and discovers the kidnapped
child. In just a couple of hours, reporters rush to the shop to interview Jae-Gu, who is seen
as a hero now, and even the governor comes by to congratulate him. Sun-Young's father shows up too,
suddenly pretending to have always loved his son-in-law just to have a chance to befriend the
governor. The rescue of the child earns Jae-Gu a hefty cash reward that he uses to finally buy the
shop, although Sun-Young refuses at first because her dad is charging them extra on purpose. Jae-Gu
is aware of this and buys it anyway because he enjoys being passive-aggressive toward
his father-in-law while they sign the papers, shaming him in front of the whole family for
scamming his own daughter. The couple also buys a nice car, but their spending doesn't stop there:
now that the town sees them as trustworthy heroes, they put nails on the road again and the business
continues to bloom. They get an electric sign for the shop, fancy clothes for both of them,
and even visit expensive restaurants, where they discuss the possibility of one day moving to
the big city. This also means Jae-Gu is getting most of the car repair business and leaving Mr.
Mun with fewer clients, which causes him to call Sun-Young to do more blackmailing, but Sun-Young
ignores his calls. From then on, a mysterious car begins following Jae-Gu again. One afternoon,
Jae-Gu is in town enjoying a beer at his usual spot when he suddenly hears some commotion and
follows a cop to the hospital, where he learns his nails have caused an accident and now a driver is
hurt. While Jae-Gu tries to deal with his guilt outside the hospital, Mr. Mun finds him and tells
him to go away before he tells everyone that this is his fault. Startled, Jae-Gu gets in his car to
go home and cries when he remembers Sun-Young's supposedly rhetorical question, which means she's
always known about Mr. Mun. Speaking of Sun-Young, she's in the middle of the road adding more nails,
causing Jae-Gu to finally have a breakdown and drag her home, where he tries to find
the money she's been saving to burn it off. Crying, Sun-Young tries to stop him and has no
choice but to confess what she had to do to keep Mr. Mun quiet. Since what it's done is done,
Sun-Young would rather enjoy the money instead of letting her sacrifice be in vain. Overwhelmed with
guilt and pain, Jae-Gu rushes to the road to take off the nails, but they've done their job well and
they're impossible to move, not to mention the sheer amount of them. The next morning,
while Sun-Young continues to enjoy her new dresses and make-up, Jae-Gu borrows
a truck to drive it down the road, hoping its weight will bend the nails once and for all.