Santiago is a man without a life of his own. In his forties, he works as a waiter for his mistress' ex-husband, with whom he has a masochistic relationship. Unable to comprehend the situation, he plots a plan to get revenge. The Yellow Line belongs to the so-called ''Catharsis Trilogy'', three films that have in common stories related to the therapeutic, the cathartic and the absolute necessity to leave behind some moral wraiths in order to harmoniusly confront and overcome life's different ups and downs: desires, fears, perversions, existential contradictions...