Mono was being trained by Victor Delgado to become a mechanic aboard El Cavador. Mono was often impressed with Victor's skills, especially when Victor was able to make a new device out of junk such as the stabilizer Mono helped Victor install on the ship's mining drill.
One day after Mono went in late as requested by Victor's mother, Rena, El Cavador was bumped by a corporate ship captained by Lem Jukes. Mono would then spend the next several weeks helping Segundo and Victor repair the ship.
When Victor decided he needed to leave to warn Earth about the Formics, Mono helped Victor modify the quickship Victor would use to travel to Luna. Victor had a hard time saying goodbye to Mono because of their close relationship. Victor also knew it was unlikely he would ever see Mono again.
Months later, El Cavador decided to attack the Formic scout ship, and contacted a WU-HU Corporation ship and Lem Jukes for help. All the women and children of El Cavador were sent to the WU-HU ship for the purpose of safety, as the WU-HU ship's job was going to be recording information from a safe distance. Mono tricked his mother into believing he went on the WU-HU ship by having his friend Zapa tell her he went to the bathroom. Mono wanted to stay on El Cavador to help the men of the crew fight the Formics. Later, Mono felt guilty for his decision after the ship's captain Concepción Querales learned that he had stayed aboard. Mono was unable to go to the WU-HU ship because of the incapability of making another high speed docking.
Mono was killed when El Cavador was destroyed by a gamma plasma exhaust burst from the Formic ship.