Bespectacled nerd Li Junwei, Qiao Renliang, and the pretty Tang Xiaolian, Li Xiaolu, are manning the night shift at the 24-hour Wang Wang Supermarket when balding lottery addict He Sanshui, [Xu Zheng], arrives, demanding to speak to the lady owner Wang Sufen, [Yang Qing]. Wang Sufen, who is not in, had typed the lottery number incorrectly more than a month earlier, which rendered He Sanshui's winning ticket useless. When He Sanshui previously asked for the ¥9500 prize, she attacked him and drove him out of the store. This time, He Sanshui returns with a stun gun flashlight and his dimwitted cousin He Damiao, a.k.a. Tire, determined to get his ¥9500 “back.”
At this moment, Li’s goofy roommate Zhu Liao, [Zhao Yingjun], who wants to record a funny prank video, storms in wearing a pantyhose over his face and wielding a knife, but is quickly tasered down by He Sanshui. He Sanshui then moves to the cashier counter and realizes there isn’t enough cash in the till. He and Tire rope up everyone else in the soundproof back room—which happens to have a full Karaoke system—and take their places behind the register, funneling the profits into their own pockets.
The hungry Tire becomes preoccupied with bag after bag of junk food (some of which has expired) and karaoke singing, so Li Junwei, nicknamed “Little Steel Teeth” by He Sanshui for his dental brace, is brought back out to help with the work. Some time later, Tang’s attempt to escape, during which she tasers Tire, is foiled by Zhu’s foolishness and a second stun gun from He Sanshui.
Wang Sufen suddenly returns to the store from her Mahjong game—clearly money-lost—and immediately begins to attack He Sanshui with a bag of weights, before Tire tasers her down. However, holding her (and her French Bulldog Wang Wang) hostage does nothing to improve business, which has been slow tonight. In an effort to boost sales, He Sanshui decides to offer a 50% discount on all items, and business quickly perks up after a taxicab chauffeur (Cao Li) helps spread the news to his colleagues. During this time, Tang discovers voyeuristic photos of herself in Li Junwei’s phone and realizes that Li likes her.
With ¥3.50 to go before reaching their ¥9500 goal (taking into account Tire’s ¥118.10 snack bill), a Guanzhong dialect-speaking, gun-toting robber—the Bandit Zhang Jiayi—on the run arrives to retrieve a diamond his partner left in the store’s ice-filled freezer. Unable to find the diamond, he takes everyone hostage and has them strip, when Yaozi—the store’s delivery man who had fallen asleep in the warehouse—barges out from the rear. The group tries to subdue the gunman but fails because He Sanshui’s stun gun has run out of battery.
When the diamond is finally discovered during the ensuing search, the dog Wang Wang picks it up and dashes outside. It’s then clear that the police have already surrounded the store: Tang had secretly texted a policeman shopper, Li Wei Jian. The gunman races back inside, grabs Tang, and points his weapon at her head. Li Wei Jian saves Tang but is shot by the gunman, who is accidentally electrocuted by a loose wire.
Some time later, the police return and learn that Li Junwei—no longer wearing a brace and glasses—and Tang are dating, while He Sanshui and Wang are honeymooning in Hainan. They also watch on TV that Zhu Liao has become a famous actor, and Tire his agent.
