Un extraño enemigo

The regent of Mexico City, Corona del Rosal, wants to weaken his main adversary in the presidential succession by getting rid of the National Security Directorate. Major Barrientos, the leader of the DNS, tries to strengthen its position and that of his boss by creating the perception that the student movement striking in Mexico City is a real threat, to then repress them violently.

The student's voice becomes louder despite their lack of organization. After the death of one of the student leaders, and with the assistance of Barrientos, the students will finally become a more cohesive force. With strengthening numbers, the student movement will increase the number of demonstrations in the city, which will subsequently be repressed by the government.

The students establish the National Strike Council (CNH), and organize one of the largest marches ever seen in the country. The government of president Diaz Ordaz is placed in the spotlight. At the same time, the CIA wants to help Corona del Rosal, a candidate to the presidential race, to carry out a coup and return the country to law and order.

Barrientos infiltrates guns among the students, to make them seem like a more threatening force to president Diaz Ordaz. Elsewhere, the CIA tries to influence the military leaders of the country to move forward with a coup and they reject their plans. Alicia, finally discovers who the government infiltrator.

President Ordaz arranges a meeting with the students through the Chief of the Presidential Office. The meeting appears to be a success, but Barrientos wants to discredit the gains attained during the meeting by creating a sense of "chaos" in the country. Beto tries to take Alicia out of the city, knowing her life is in danger, he soon realizes that Barrientos' eyes are everywhere.

Corona del Rosal convinces the president to use moles during the "March of Silence," a march organized by the National Strike Council, in order to put an end to the organization. Barrientos wants to thwart his plans by provoking a fight during the march. However, seeing how well prepared the students were, Barrientos has to put a stop to his plans and re-evaluate his methods.

The Army, at the behest of the President, takes over the UNAM. Dean Barros Sierra resigns his post, causing greater political pressure on the president to start dialogue with the students. Meanwhile, Barrientos plots a different plan of violence and riots to corner the President and force him to order a definitive solution to the student problem.

The negotiations between the students and the government are moving forward. Corona del Rosal still plans to arrest the leaders of the National Strike Council during a planned march. Although their plan is to arrest them without casualties, Barrientos has placed snipers around the plaza, in an effort to create a brutal crossfire between the students and the military.