Inspired by true events, the film chronicles the story of Sisoy Salas, a corrupt journalist seeking justice for his colleagues, and convict Roman Rubio, a hired gun who is regularly brought out of prison to perform assassinations.

On The Job is about the ambitions and passions of four men trying to make a living, for themselves and their families. It shows the parallels between two prison inmates who are contract killers, and the two agents of the law investigating the murders. As they get caught in a web of machination of corrupt government officials, their jobs lead them on a head-on collision against each other with their loved ones as collateral damage.