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 increase 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 investigate 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 and the Unit suffer some setbacks that compromise their police work, but unite their members.

The Unit's inability to anticipate the plans of the terrorists, who are getting closer and closer to achieving their objective, creates further tension within the team.

When events push the members of the Unit to the limit, they are forced to make difficult decisions to collect themselves and regain control of the situation.