The show revolves around two men connected by a heart transplant: the donor, Rodrigo Ugarte (Juan Diego Botto), and the patient, neurosurgeon Álex Puga (Pablo Derqui), who starts seeing Rodrigo's memories in the form of nightmares and hallucinations after the operation. Rodrigo was a journalist who was investigating a series of disappearances, and whatever he had found apparently cost him his life. Álex discovers theories about the "memory of the heart", and decides to try to solve the mystery of Rodrigo's death with the help of Lara Valle (Meritxell Calvo), an aspiring young journalist he used to mentor.
Tropes seen in this show:
- Arc Words: Rodrigo's final words to Lara were "choose wisely who you trust", right after he had handed her his gun. She writes these words at the top of her cork board when she starts investigating his death... and believes Álex when she sees the very same words written down on his notebook of Rodrigo's memories.Lara: Son of a bitch... It's true.
- The Big Damn Kiss: Álex and Marian get theirs on episode 4.
- Break Her Heart to Save Her: Rodrigo was well aware of how dangerous his investigation was and got away from Marian so that whoever was behind the disappearances wouldn't go after her or their children.
- By-the-Book Cop: Rodrigo's informer in the police force, Santiago Ariza. When Lara goes to him after her house was broken into and the flash drive Rodrigo had left for her was stolen, she is unable to prove it, and he simply insists that there is no evidence of a break-in, and that "without evidence there's no case".
- Chekhov's Gunman / The Man Behind the Man: The mastermind behind the disappearances is Carlos Meyer, the son of the owner of the Meyer Clinic that nearly hired Álex.
- Crazy-Prepared: The killer seems to have everything planned out. His car is identified by the police? No problem, he has a reserve one. A facial composite of him has been made? He was wearing a wig and contact lenses as part of a disguise.
- Drugs Are Bad: A point that is driven home with Álex's drug-induced heart attack.
- Dr. Jerk: At the beginning, Álex acts like a complete jerkass to some of his hospital co-workers, as he's on his way out and ready to move to one of the most prestigious clinics in Madrid.
- Functional Addict: Why Álex could do more than half of the operations in his department: the drugs he took allowed him to stay active for longer. Eventually it catches up to him.
- Genre Blindness: For someone as used to dealing with cunning, dangerous criminals as Ariza should be, not checking yourself for microphones after a stranger bumps into you right before you were going to interrogate the boss of the prostitute the killer is looking for is an inexplicable mistake.
- Intrepid Reporter: Rodrigo got himself into a really big investigation with the disappearances case, and it's heavily implied that he was murdered because he knew too much and was still willing to go all the way with it.
- I Have Your Wife: Towards the end of the fourth episode, the bad guys sneak into Lara's house and threaten to kill her girlfriend unless Álex and her stop meddling with their plans.
- Master of Disguise: The killer is one. At the end of the third episode, he removes his wig and colored contact lenses, and deliberately burns his wrist to erase the tattoo he had been identified by at first. And on the fourth he manages to pose as a police agent to get to the prostitute.
- The Mirror Shows Your True Self: Álex starts to constantly see Rodrigo staring back at him from mirrors.
- Nothing Personal: In the second episode, the as-of-yet-nameless Serial Killer tells this to Irene, his contact with whoever is paying him, after staging a kidnapping to her to get the money he feels he's owed.
- Reverse Whodunnit: The series doesn't take long to introduce the killer, after that the question is if he will actually be caught, since he always seems to be one step ahead.
- Stalker with a Crush: Álex also experiences Rodrigo's own feelings after the transplant, so he develops a powerful attraction towards Marian, Rodrigo's widow, that causes him to start becoming this.
- Tested on Humans: The disappeared people are healthy people kidnapped to test on them a substance called BN23.
- Unfinished Business: The reason why Álex sees the memory of Rodrigo's heart.Dr. Escudero: Some hearts leave debts. Solve those debts and the nightmares will disappear.
- You Have Outlived Your Usefulness: Carlos and the murderer kill Tania, the prostitute, after she has told them everything she knows about Álex and Lara.
