Julio Olmedo, a young man of humble origin, travels to Cantaloa to visit his sister Cristina, one of the maids of the Gran Hotel. But when he arrived, Julio runs into an unpleasant surprise: it has been more than a month since anyone has known anything about his sister after he has been expelled from the hotel for an alleged robbery. Convinced that there is something dark about Cristina's disappearance, Julio decides to stay at the Gran Hotel. With the help of Andrés, one of the waiters, and hiding that he is Cristina's brother, Julio manages to work as a waiter at the Gran Hotel with the intention of investigating what happened with his sister. But in the course of his investigation, he will meet Alicia, an elegant and distinguished woman with whom Julio already crossed before taking the train to Cantaloa and who is neither more nor less than the daughter of Doña Teresa Alarcón, the owner of the Gran Hotel.

Julio runs into the final test confirming that his sister has not left the Gran Hotel; Someone has tried to burn Cristina's bloody clothes in one of the hotel kitchens. A test that seems to confirm Julio's suspicions; Cristina is dead ... but ... who was to blame? And ... does this have something to do with the young woman who has just been killed in town? Meanwhile, the Alarcón family, attends to the evolution of Sofia who, after having fallen down the stairs, fears for the future of her son.

Julio is closer than ever to find out who murdered his sister and the main suspect is none other than Diego, Alicia's fiancé. Without proof to prove it, Julio will only have one possible path for his investigation; find the author of the anonymous Diego, the only person who can shed light on the death of Cristina. However, in parallel, Detective Ayala is following another clue: that of the weapon with which Jimena's murder was committed. The famous gold knife that appears in Javier's room, which was also the last person with whom the prostitute was killed. All indications point to the young Alarcón.

Julio's investigation into the death of his sister Cristina turns around after a serious incident. Aided by Alicia, the young man will have to check his belongings for a test that will guide him to the murderer. Meanwhile, Ayala is convinced that Pascual is the murderer, so he allows Javier to get out of jail and return to the hotel. The young Alarcón has managed to get rid of his problems once more, but the tranquility does not last long. Sofia and Alfredo also get things upset. The marquis wants to organize a hunt at the hotel to gather the great aristocrats. But Diego is not willing for Alfredo to take any merit.

Detective Ayala has discovered Julio's true identity and appears at the hotel looking for the young man. Meanwhile, at the Gran Hotel, Alicia and Diego's relationship seems to begin to consolidate after Diego saved the young woman from dying at the hands of Pascual. But the arrival of an old family acquaintance will awaken Diego's insecurities that he is willing to fight for Alice until the end. It is not the only problem facing the hotel manager; Sofía and Alfredo gather the courage to start fighting Diego and make Alfredo take his rightful place inside the Gran Hotel. For his part Eugenia, Javier's fiancee, discovers young Alarcón in bed with another woman. Eugenia's anger is unleashed upon discovering that it is about Mercedes, her own sister.

Julio will try to run away from Ayala, who is looking for him for being a murder suspect. After the discovery that Julio is being wanted for murder, Alicia warns him that Ayala will go after him ... Julio must prevent the police from stopping him while continuing to investigate the death of his sister. The appearance of one of the objects he saw among the girl's things in the Grand Hotel will revive the investigation. The General, after losing a daughter and having another seriously injured because of Javier, challenges him to a duel from which young Alarcón will try to escape by all means. Sofia, meanwhile, has discovered that the son who expects Bethlehem is possibly from Diego. Sofia must stop her husband's impulses to reveal this information to Teresa while she starts looking for ways to get another baby. Ángela takes advantage of the arrival of a new maid at the hotel to try to break the relationship between Belén and Andrés definitely.

Julio just got a big surprise discovering that his sister is still alive. After the excitement of the reunion, there are many questions which Cristina must answer. Why is she still alive? What has happened? Why has it been hidden all these weeks? What relationship does his supposed death have with the other crimes that have hit Cantaloa? Cristina's presence will resolve all these issues but will also unleash new questions and dangers that, far from solving everything, will cause serious problems for both her brother and Alicia. Meanwhile, at the hotel, Diego's detention, accused of Cristina's death, leaves a power vacuum that immediately unleashes a struggle between Alfredo and Javier.

After the death of Cristina, Teresa is determined to make it appear that this death has been an accident to end the problems caused by Cristina Olmedo once and for all. But, both Detective Ayala and Julio will begin to suspect those manipulations and try to discover what really happened. The hotel is not only shocked by the death of Cristina Olmedo, but by the return of Diego Murquía. The former director will do everything possible to recover his former position and the commitment he had with Alicia ... something that affects her very deeply. She has already kissed Julio and feels closer and closer to him. Meanwhile, in the world of service, Bethlehem is still facing Catalina, whom she sees as a threat to all her interests, and will not stop until she can get rid of it anyway.

Alicia is about to run away with Julio, but a new revelation around Cristina's death makes him want to return to the Grand Hotel to try to find out who killed his sister. That hurts Alicia, who feels rejected, and brings her closer to Diego, who, shrewdly, maneuvers to seduce her and make her voluntarily go to the altar, as the wedding date is getting closer. Time is running out and Julio will be forced to choose between the love he feels for Alicia or discover who his sister's murderer was. In the Alarcón family, things are not easy either. It is increasingly difficult for Sofia to fake her pregnancy before her husband, and Javier is in the hands of Diego, who has discovered his business with the smuggling spirit. Meanwhile, Belén, once free of Catalina and much better located in the Gran Hotel, rejects Andrés ... until something totally unexpected happens that turns the situation around and makes everything change, not just for her, but for all who live in the Grand Hotel.