After a presentation of the inhabitants of the building of the staircase 15, we are interested in the strange behavior of Mr Blouin, innocuous chief accountant. But why does he fix eggs with scotch tape and measure the trees on the avenue?
Mr Blouin takes part in a press competition. He wants to win the first prize, an apartment, to offer it to his daughter Sophie. Other tenants of the building, attracted, also embark on the adventure.
Blouin and his accomplices, Goujon and Lamenoise undertake to kidnap the deer head that adorns the office of Mr. Letourneur the director of Blouin. The experience turns out to be perilous, it then remains to fill the cupboard.
The test of the day, for tenants of the 15th, is to find the time it takes to set up a patrol tent. but above all they must find a welcoming lawn, coordinate well and above all not be pawned by spies who also want to win the competition.
Blouin, Goujon, Niko and Lamenoise have a new test for the competition. Meanwhile, Blouin's son, tries to approach his pretty neighbor, Valérie Janniau. But that's without counting another pretty heart of the 17, the son Nikolovich.
"A young peacekeeper hears a gunshot. He rushes forward, after which he will have to change his shoes. Why?" Such is the enigma submitted to the reflection. Gérard and Johnny would like to solve it to please Valérie.
How do you recognize an opera aria from a series of photographs of a singer? Niko, Lamenoise and Blouin go to the opera, while Gérard has to face new disappointments in the face of Lemaire and Johnny's daring towards Valérie.
Six o'clock in the morning, wake-up time for Blouin, Boulanger, Goujon, Niko and the Lamenoise. While Dora occupies the garbage collectors in the cafe, the fine team "borrows" a garbage truck from them to answer the question of the day.
Reconstruction of a crime scene in the Nikolovsky living room for the purposes of the competition: Goujon takes himself for Maigret, Niko plays the victim and families are called upon to take on the roles of the suspects.
New day, new puzzle: the staircase 15 team does not give up in front of this genealogical enigma. Always in competition to please Valérie, Gérard and Johnny fight.
New team meeting, this time for a dance event. The atmosphere remains tense following the fight between Gérard and Johnny. Pushed by his sister, Gérard embarks on writing a letter to declare himself to Valérie.
"What is the price of these items?" asks the newspaper. The members of the team leave to investigate, but the objects in question are unusual. Valérie ends up finding Gérard's letter before going out to dinner with Lemaire.
"How many cauliflowers in this pile?" To answer the question of the day and after having tried the arithmetic method in vain, Boulanger, Blouin, Lamenoise and Goujon set off on an expedition to Les Halles for a "live" experience.
The inhabitants of 15 must answer a question about hitchhiking: for whom will motorists stop the fastest? Valérie, Sophie, Miss Janniau, Dora, as well as Mathilde and her granddaughters Nadine and Joëlle, take on the roles of hitchhikers.
Goujon, Blouin and Lamenoise miss their "motor bike operation" miserably, and come home angry. Following a mockery from Johnny, Valérie and Gérard have their first romantic quarrel.
Blouin continues and tries to answer the question "A major starts with his left foot on the first bar of the chorus of the Bridge of the River Kwai, on which foot will he arrive at the last note ? ". Blouin put the building in turmoil.
Today it is a question of finding out at what time a photo of a statue was taken, from its shadow projected on the ground. Boulanger helps Blouin, still determined to continue the competition alone, but they encounter the rain.
For the competition, Madame Janniau and the Boulangers unite their efforts to find the anomaly in the outfit of an 18th century soldier. Gérard, unhappy, writes a letter to Valérie and disappears .
It is panic in the building since the disappearance of Gérard. The neighbors show solidarity with the Blouin family. Valérie finally understands the reason for Gérard's anger.
The tenants resume the competition. They have to guess the number of cars of a train photographed in a curve. The team is mounting an expedition to extract information from the station master.
For today's challenge, the fine team of 15 must determine if a prisoner handcuffed to a chair can escape through the window in 20 seconds. Following a joke, Blouin finds himself handcuffed to Goujon .
The last question of the competition leads the tenants to a castle. They have to find from which window the photo of the newspaper was taken. The team will deploy all its imagination to enter, despite the presence of the guards .
The competition ends and everyone begins to dream. To fill out the response forms, the team meets under the dictation of the teacher Boulanger. The group does not realize that Mr. Lemaire is spying on them .
The competition is over. We just have to wait for the results. The Blouin invite their neighbors to celebrate the engagement of their son Gérard with Valérie. The celebration is crowned by the proclamation of the results.