During a routine operation, the Spanish police arrest the world's most wanted terrorist. This puts Spain in the crosshairs of jihadist terrorism.

The lack of resources and the pressure to catch the terrorists increases tensions within La Unidad, whose members also have to deal with the personal problems brought about by their exhaustive dedication to police work.

The disappearance of an agent infiltrated in the terrorist cell triggers all the alarms. The Unit investigates around the detained terrorist leader to detect the connections and next steps of the terrorist cell that threatens Spain.

Events are rushing on both sides of the border. The terrorists receive support, the Unit suffers some setbacks that compromise its police work but that unite, personally, its members.

The Unit cannot anticipate the plans of the terrorists, who are getting closer and closer to achieving their objective, something that affects and further tenses the team led by Carla.

The latest events put the members of the Unit to the limit, who are forced to make difficult decisions to collect themselves and regain control of the situation.