Kingdom of Valencia, 1079. A knight is fighting off a group of Moorish soldiers, brutally slicing and stabbing through them. All of this is being filmed by a camera, held by a man trying to stay hidden in the bushes. This man, and another, try not to call attention to themselves, but their moving and the camera are noticed by the knight, who approaches the two of them... opening himself to be killed by another Moorish soldier. As the latter leaves, the two men approach the knight's body and one of them scaredly claims they have just killed El Cid.
In the present, it's been a few months since the 1924 mission and the related debacle caused by Irene. Lola Mendieta is in prison. However, today has good news: Julián rejoins the Ministry after spending some time resting and in psychological treatment after the shock of learning his accidental role in his wife's death. As the characters share something of what they have been doing in this time - including the fact that Amelia and Alonso have watched the Terminator films Julián had recommended - Salvador calls them to his office.
A recent archeological excavation in Valencia has found several bones that could belong to Rodrigo Díaz de Vivar, El Cid Campeador. Of course, the problem is that these are supposed to be in the Burgos Cathedral, and the Ministry was behind the tests to check they were: obviously, either set must belong to an impostor, but which ones? So, they must travel to 11th Century Valencia and find out the truth. However, Julián will not be going with them, as he is still not yet allowed to carry out missions. While Julián is asked to take charge, on a temporary basis, of the Ministry's medical station, another person will replace him for this mission: Ambrogio Spinola, much to Alonso's joy, although Spinola is not happy to learn that Amelia is in charge of the mission.
After coming out in the year 1099 (and solving a small confusion brought by meeting a Muslim Ministry agent, whom Alonso believes is the enemy) the three travel to El Cid's camp (while Spinola clashes with Amelia over leadership and personal issues that Amelia puts an end to rather sharply), and meet a group of Christian knights in the way... led by El Cid himself (Sergio Peris Mencheta). This short encounter is interrupted by an ambush by Almoravid soldiers, and El Cid proves his worth in the fight (while Spinola shouts "¡Yipi-kai-yey, hideputas!", a Shout-Out to Die Hard and Actor Allusion, as Spinola's actor is Bruce Willis' Spanish VA). The attack stopped, El Cid invites the trio to his camp, an offer they accept.
That night, during dinner, in which the Trio meets Rodrigo's wife, Jimena, they share stories about their respective pasts... but Amelia begins to feel doubts about El Cid's true identity: the events he refers to were historically known not to have happened, but only appeared in Spanish cantar de gesta El Cantar de Mío Cid. The following day, taking advantage of Rodrigo being away, Amelia sneaks into his tent, and she finds a copy of El Cantar de Mío Cid, along with several other modern objects and, most importantly, a photograph where Rodrigo appears with other modern men, standing in what is, for her, Salvador's office. However, Jimena has seen her sneaking around, and tells Rodrigo, who places the trio under arrest.
Rodrigo meets with the trio while they are in jail, and, after talking with them, decides to reveal the truth: his real name is Rogelio Buendía, and he is an agent of the Ministry of Time, from the late 1950s. As preparations to make El Cid went on, Charlton Heston asked to meet with reputed Spanish historian Menéndez Pidal, as he needed information so he could better play his role, but, after a rather awkward conversation (in which Heston innocently asked if El Cid used guns and if he was related in some way to Christopher Columbus) which dealt little of use, Menéndez Pidal requested the Ministry to film a documentary of El Cid's life - which led to the latter's death in 1079, caused because Rogelio distracted him. Desperate to make amends and prevent this rather serious loss of such an important historical character, Rogelio replaced Rodrigo, and has been in this mission for more than two decades, unable to return to his time to meet his family again. Since he knows his death will come some time soon, Rogelio tells the trio that he has given orders for them to be freed after his death within a month, and leaves to do battle.
Unfortunately, a catastrophe takes place, and Rogelio is mortally injured in a skirmish: he requests the trio be freed. While Amelia discovers that Jimena already knew her husband was an impostor (apparently, the original was less noble than what the legend indicated), Rogelio is trying to get back on his feet, because he knows a battle will come soon, but he is clearly unable. So, Alonso decides to replace him by putting on his armor so no one will see his face, thus giving birth to the legend of how El Cid won a battle after dying. While Rogelio dies, Alonso (squeeing over being able to use the legendary Tizona) leads the defenders of the city of Valencia in battle against the invading Almoravids.
The trio returns to the present to report on the success of their mission (with Salvador asking about the rather strange bruises and cuts Alonso and Spinola are sporting), but then they find out that Julián, still reflecting on his inability to save Maite, and after meeting another agent that tells him about his past missions, has decided to go to a past time where he can use his medical knowledge to help the people there as best as he can.
A minor scene reveals Susana Torres (who first appeared a few episodes ago) is starting to keep a closer eye into the Ministry...
