[1] The series focuses on two civil guards of very different backgrounds who have to work together solving relevant crimes.
[3] Olmos is a corporal of the Civil Guard's Public Order and Prevention service who works in the station of his birthplace, Ezcaray, a small peaceful town in La Rioja.
Robles is a lieutenant of the Rapid Reaction Group, one of the most prestigious units of the Civil Guard, an urban and modern officer.
They see themselves forced to work together if they want to solve the international case which, as luck would have it, has united them in this town in La Rioja, the serial murder of a group of mercenaries.
In season 2, both guards have to work together in order to solve another important crime, which includes the death of Robles' parents, the assassination attempt of a Spanish high-ranked NATO politician and an international corruption plot related to an important arms trade enterprise.