Follows the professional and personal lives of the staff of the fictitious Hospital Central in Madrid.

The story is settled in the Middle Ages when three monotheistic religions coexisted and fought for power in the Spanish Peninsula: Christians, Muslims and Jews. The series mixes action, intrigue and love in the Castilian capital of Toledo. It shows us about all those who lived in the walls of a city full of ups and downs, labyrinths and shady hiding places.

In a society, the proud and arrogant Golden Age Spain, riding blind towards the end of the Empire and in which the honor and loyalty are all, a Spanish soldier who has travelled Europe fighting under the flag of "Tercio Viejo de Cartagena", survives in the Austrias' Madrid as a mercenary swordsman hired four coppers on request. Brave, honest and loyal man, Diego Alatriste will be involved in intrigues and conspiracies of various kinds that require him to make good use of his steel.

During a long weekend, Marina and Julian murdered and dismembered a young married couple. Veronica, the agent in charge of the case, dives into their messy memories to uncover the reasons that led them to commit the brutal crime.

Many prisoners convicted of rape, murder and terrorism are released before serving their full sentences. Hours later, one of them is killed. Detectives Mora and Nieto take on the case.

To remain independent of her father, who is a stolen goods trafficker, a newly widowed single mom joins her late husband’s gang of smash-and-grab thieves.