Lázaro and Sabino, employees of a large furniture store, fall in love with Laura, a new young and naive employee, who accepts their love. The trio lives a happy engagement. In the big store is planned a sensational advertising campaign with the bed "Eternal happiness," to be launched on New Year's Day. Lázaro and Sabino have to give the last touches on New Year's Eve. When they leave, they enter the exhibition truck and lie down on the bed. When they wake up in the morning, they are surrounded by a crowd and a scandal is organized.

Evelino Galindo, the serious owner of a porcelain store, argues with the womanizer jeweler Orcajo for an insignificant game of dominoes. Evelino, enraged, challenges him the next day to a duel in the gym. But after meditating a bit he starts to get scared. That is why, with the help of his friend Leoncio, he sharpens his wit to find a way to escape from combat. However, the situation is becoming more complicated.

Don Mendo, Marquess of Cabra, gallant and dashing knight of medieval Castilian, is also a virtuous mandoline player and a specialist in climbing towers. But he has a bad run, all played and all lost at seven-thirty (card game), and lost his honor playing in his latest escalation of love to the apartment of his beloved and beautiful Magdalena. Don Nuño Manso de Jarama, father of Magdalena, has pledged the hand of his daughter to the Duke of Toro, and surprises Don Mendo in the room of Magdalena. To save the honor of his beloved one, Don Mendo says that no love has led him to the Tower, but he has climbed to steal. Magdalena is clean of all suspicion, and he is condemned to die buried in the castle wall. The Marquess of Moncada and other noble gentlemen, all friends of Don Mendo, facilitate his escape.