One day, a dead body is found at an apartment near the supermarket. Finding this murder odd, Dae-sung, his mother, and his girlfriend Ah-hee gather around to find the real murderer, starting by looking through the receipts of the market.
The police begin investigating the body that Dae-sung and Nunchucks Grandpa found. However, Dae-sung becomes nosy again and starts digging into this by himself. His way of investigation is looking into the shopping list of the victim. With the clues that he obtains from there, he notices a suspicious person within the neighbourhood.
Daesung Mart develops into the great MS Mart thanks to Myung-sook’s bravery and Dae-sung’s smartness. Although Dae-sung continuously fails the civil service exam and is about to get dumped by Ah-hee, his love for his mother’s supermarket does not change. He determines to work there as a cashier, but runs into a case that changes his life as an employee of MS Mart.
Now that Cheon-kyu stabbed the detective, it is certain that he is the murderer. He then flees with Yool where no one can find them. However, Yool comes up with a clever idea to give a clue to Dae-sung. Without any help from the police force, the employees of MS Mart rush over to save Yool from her father. The hostage situation is dangerous, but everyone risks their lives for Yool.
Five Dollars finds and takes what Yool hid in her secret place. But the chairwoman finds the two and saves Yool from the criminal. As many people now think Five Dollars is not the killer, new suspicions lead to someone within the supermarket. Seeing how Veggie seems to be the new target, Meat becomes the number one suspect. Although Dae-sung does not want to believe so, Meat must be investigated.
The chairwoman miraculously survives the fall. Although she is in horrible shape and in a coma, she provides a clue to Products. Meanwhile, Veggie is still going through a hard time. Even though there is no clear evidence, everyone strongly believes that Meat is the one harassing her. However, new events occur and bring up new information regarding the murder cases.
As Products has been acting suspiciously, Dae-sung and Myung-sook tail her to see if she is the killer. However, Products is not the only suspicious one. Although it is clear that Yool is being abused by her father, she denies help. Dae-sung tries to think why Yool is denying help and confidently says that Dae-sung is not the murderer. This allows him to come up with another lead.
People now know that Nunchucks Grandpa is the notorious five-dollar bill counterfeiter. Although some evidence show that Five Dollars is the murderer, it is not enough to prove his guilt. Dae-sung is upset that the counterfeiter might be set free. However, he witnesses someone else at the murder scene who definitely seems suspicious.
Five Dollars eventually becomes free from being a suspect. However, the police now suspect Dae-sung. To clear his name, Ah-hee, Dae-sung, and Myung-sook investigate everyone in the neighborhood. Currently, although their biggest suspect is Fish, Products also seems to be very busy right after the murders occurred. With every possibility in mind, the supermarket investigation begins.