Efrain has hinted he was a priest in Tijuana, Baja California, prior to the beginning of the apocalypse.
Sometime after the beginning of the apocalypse, Efrain became a vagabond who traverses the streets of Tijuana caring for those in need. At some point after Dante's take over of the Gonzalez Dam, he and Lola, the head of the municipal water utility, set up a secret arrangement for water to be supplied to a tucked away fountain every Tuesday at 5 PM. Efrain distributes the contraband water to the needy in an old rickshaw, notifying survivors of his presence with a recording that repeats "agua, agua, agua."
After Daniel passes out, he's awakened and pulled out from under the car by Efrain who sees Daniel's charred legs and warns him he'll die if he doesn't get help -- and water. Efrain leads Daniel to a shed with a dry water fountain. Daniel is skeptical that the water will come, but at exactly 5 p.m., water begins to flow. Daniel laps it up thirstily, and Efrain fills his jugs while explaining that water miraculously flows from the fountain at 5 p.m. every Tuesday. Incredulous, Daniel wonders who this man in front of him really is. Efrain, revealing his penchant for humor, provides a little comic relief: "I'm the fifth Beatle, and you?" Efrain then loads Daniel into a rickshaw and peddles through the zombie-filled town, expertly dodging the Infected along the way. Efrain delivers some water to a family. They scoot out of sight as a vehicle of armed men -- whom we later learn are ruled by a cruel big shot named Dante, who controls the water supply in this godforsaken place. Daniel fades in and out of consciousness as Efrain and his friend Lola debate how to treat Daniel's infected leg. When he awakens, Lola is pulling out a knife. He screams in pain as she scrapes off the charred skin with a blade. Eventually, he feels good enough to bond with Efrain and share some whiskey with his new friend. A trained barber, he gifts the homeless man with a needed haircut. Efrain is captured by Dante's henchman and brought back to the dam to be tortured for information as to who has been secretly sending water to the fountain. Daniel tells Efrain if he confesses both he and Lola will be killed, but if he stays silent then Daniel will kill Efrain quickly out of mercy. As Daniel tortures Efrain on Dante’s command, he asks Efrain for forgiveness. Efrain responds: “Again?” Lola confesses to save Efrain and the two along with Victor, Pablito and Everardo are taken to the edge of the dam. Dante plans to toss all five off the dam to make an example of those who steal water from him. After Pablito is thrown off the dam to his death Daniel intervenes killing Othón, J.C. and Dante, thus freeing Efrain and the others.
This list shows the victims that Efrain has killed:
Efrain saves Daniel's life on the streets of Tijuana and nurses him back to health. They become friends and bond when Daniel gives Efrain a much-needed haircut. Daniel repeatedly asks Efrain, a priest, for forgiveness, which Efrain is unable to provide. Daniel ultimately saves Efrain's life by killing Dante and his henchman before they could throw him off the Gonzalez Dam.
Lola and Efrain are close friends and work together to provide water to the needy behind Dante's back. Lola deeply cares about Efrain and confesses to routing water to the fountain to stop his torture at Daniel's hands.