Pascual León, a retired 65-year-old man, starts an elaborate plan of revenge after being diagnosed with Alzheimer's. Meanwhile, Jimena Guerra, a policewoman, finds a mysterious message addressed to her at the crime scene.

Jimena begins the investigation on the Judge's murder. Tired of the attacks from the press, she decides to confront Francisco Pira, while Pascual carries out the next stage of his plan, not without some surprises.

Pascual recovers from a health problem and continues with the next stage of his plan. Meanwhile, Jimena Guerra makes new discoveries: it is the work of a serial killer and Asunción de la Sal seems to be a key piece in the investigation.

Pascual kills his third victim and meets with an old friend, millionaire Olmo Bonete. During her trip, Jimena discovers some shady secrets about her family and the town's past.

After finding more messages in the new corpses, Jimena shares her theory with Tolsa and they travel together to Asunción. Pascual continues with his plan, while secrets about Olmo are revealed.

Jimena investigates the house fire in Asunción, while Pascual proceeds with his list of murders. However, unexpected events cause him to make some choices that aren't part of the plan. A new lead about a killer "cat" appears.

Pascual's Alzheimer's advances, so he decides to go to Asunción to speed up his plan. Jimena finds a key element for the investigation which could solve the mystery surrounding the crimes.

Pascual travels with Nuri to Asunción and continues with the murders, although the accumulated lies won't be easy to handle.

Jimena discovers the truth about Rebeca's suicide. Meanwhile, the number of deaths increases. Despite some obstacles, Pascual intensifies his plan of revenge and unfolds the final stage.