"The past" is the story of Rimini (Gael Garcia Bernal), a young translator, whose 12-year long marriage with his high school love Sofia (Analia Couceyro) comes to an end. The polite way in which they conduct the separation concludes once he starts dating Vera (Moro Anghileri), a young 22 year-old model who -the minute she sees Rimini being violently kissed by Sofia- dies after a bus runs over her.
When, about a year later, having now recovered, he marries Carmen (Ana Celentano), his translator colleague, a mysterious traumatic amnesia wipes out his memory of the languages he translates. With Carmenīs help, Rimini tries to adapt to the uncomfortable role of a dependent husband. The birth of their son -Lucio- helps lift his spirits.
But the marriage is wrecked when Sofia, in a moment of madness, kidnaps the coupleīs baby for a few hours, after luring Rimini to a seedy hotel. Rimini looses not just his wife: he is no longer allowed to come close his son.
Rimini, the once brilliant translator and ladies man, becomes a mediocre personal trainer and an object of the sexual whims of Nancy, a rich and vulgar woman. Seeing her with another man strikes a jealousy crisis in Rimini: he tries to smash her car, and ends up in jail for it. It is Sofia who posts Riminiīs bail and sets him free. Now his ex-wife is the new age leader of the Adele H. Institute, a womenīs group for "ladies who love too much". She displays him to her disciples as a trophy, as proof of the efficacy of her theories on the power of memory in helping couples reunite.
During one of Sofiaīs group sessions, an encounter with -and desire for- an unknown woman, makes him realize that not only has he recovered his lost knowledge of languages, but also that he is newly able to fall in love.
