La cita célebre que inicia está película es sobre la teoría del caos; el aleteo de una mariposa podría causar un tifón al otro lado del mundo.

Dentro de una oficina el que parece ser nuestro protagonista escribe una carta súper apurado mientras lo buscan, dando una nota acerca de que ojalá pudiera volver al pasado para arreglar lo hecho y salvarla.

Ahora estamos en un suburbio muy tranquilo y pintoresco, esto es trece años antes de lo ocurrido en la anterior escena; un joven Evan está jugando con su perro mientras su madre arregla el auto para llevarlo a la escuela, un poco preocupado el pequeño evan, le pregunta a su mamá si su padre podrá ir asistir a la escuela ya que colocarán fotos pero su madre le confirma la respuesta que ya estaba pensando evan, y es que no, es peligroso para su padre asistir y no habrá más discusión de eso.

Parten a la escuela ya que aparentemente la madre de evan es una excelente mecánica. Al llegar a la escuela evan baja del carro pero si maestra cita a su madre urgentemente porque así lo dice ella y cito "debería ver esto" y es que la maestra hizo una actividad de dibujos de lo que quisieran ser de grandes, todos estuvieron muy normales hasta llegar al de evan, que fue él sobre unos cuerpos sin vida de unos nazis, alarma a su madre y a la maestra por supuesto. La madre de Evan pide llevarse el dibujo y la maestra accede, suponemos será para no llamar la atención de más personas.

En la noche su madre lo lleva al psiquiátrico del lugar y aunque él refunfuña no se puede oponer, angustiada mientras le hacen un examen a evan su madre habla con el doctor, diciendo que ojala no haya heredado la enfermedad de su padre; el doctor le da consuelo que muy seguramente el examen dará negativo que lo mejor que podría hacer es darle un diario y hacer que escriba todo lo que suceda en su día para estimular su memoria. Y así mismo sucede.

Ya en su casa evan escribe en su diario lo que será su día mientras su madre saldrá a trabajar, solo busca su bolso y cuando pasa por la cocina está evan parado con un cuchillo en la mano, aunque está claramente ahí despierto reacciona y no sabe qué ocurrió y su madre solo se preocupa más y el igual. De todas maneras salen a casa de su amigo como lo tenían planeado y al llegar los recibe el papá de estos, una niña y un chico. Emocionados porque papá había comprado una cámara nueva e iban a aparecer en una película y evan sería la estrella de este film… El siguiente recuerdo de evan es estar en el sótano desnudo junto a su amiga mientras su padre los grababa y le hacía sentir terrible que ella ni siquiera le respondía pero era lógico que algo mal había pasado y él no podía recordarlo.

Pasamos a la madre de evan en el doctor recibiendo las noticias de que evan no tiene ningún tumor o así, que tal vez todo sea ocasionado por estrés y un complejo de no conocer a su padre así que el doctor y la madre de evan coinciden en que ya es propicio que evan lo conozca, solo debe sedar a Jason para que todo sea no tan alborotado y así lo harán; el 15 de abril están en el psiquiátrico para hacer esta visita.

Evan pasa primero y se siente en la silla y justo frente a él entra su padre, jason, el cual está súper dormido y es acompañado por un enfermero y un guardia y le dice que no muerde a evan porque parecía un poco asustado, parece ser un tipo muy bueno hasta que de pronto evan despierta del trance y está jason encima de el ahorcandolo, diciendo que es la única manera, el guardia lo noquea quitándoselo de encima de evan, su madre entra desesperada y protege a evan aunque jason ya está muy mal, el golpe fue muy contundente y muere frente a evan…

English

The famous quote that opens this film is about chaos theory; the flutter of a butterfly could cause a typhoon on the other side of the world.

Inside an office the one who seems to be our protagonist writes a letter in a hurry while he is being searched, giving a note about how he wishes he could go back in time to fix what has been done and save her.

Now we are in a very quiet and picturesque suburb, this is thirteen years before what happened in the previous scene; a young Evan is playing with his dog while his mother fixes the car to take him to school, a little worried little Evan, asks his mom if his father will be able to attend the school since they will place pictures but his mother confirms the answer that Evan was already thinking, and that is no, it is dangerous for his father to attend and there will be no more discussion of that.

They leave for school as apparently Evan's mother is an excellent mechanic. Upon arriving at the school, Evan gets out of the car, but if the teacher summons his mother urgently because she says so, and I quote "you should see this" and the teacher did an activity of drawings of what they wanted to be when they grew up, all of them were very normal until they reached Evan's, which was about the lifeless bodies of some Nazis, alarming his mother and the teacher of course. Evan's mother asked to take the drawing away and the teacher agreed, presumably so as not to attract the attention of other people.

At night his mother takes him to the local psychiatric hospital and although he grumbles she can not oppose, anguished while they make an examination to Evan his mother talks to the doctor, saying that hopefully he has not inherited the disease from his father; the doctor gives him comfort that most likely the test will be negative and that the best thing to do is to give him a diary and make him write everything that happens in his day to stimulate his memory. And so it happens.

At home evan writes in his diary what his day will be like while his mother goes out to work, he just looks for his bag and when he passes by the kitchen there is evan standing with a knife in his hand, although he is clearly awake he reacts and doesn't know what happened and his mother only worries more and so does he. Anyway they go out to their friend's house as planned and when they arrive they are greeted by their dad, a girl and a boy. Excited because dad had bought a new camera and they were going to appear in a movie and evan would be the star of this film... evan's next memory is of being in the basement naked with his friend while his father was filming them and it made him feel terrible that she didn't even answer him but it was logical that something bad had happened and he couldn't remember it.

We move on to evan's mother at the doctor receiving the news that evan has no tumor or so, that maybe it is all caused by stress and a complex of not knowing his father so the doctor and evan's mother agree that it is now propitious for evan to meet him, he just has to sedate Jason so that everything is not so rambunctious and so they will; on April 15 they are at the psychiatric facility to make this visit.

Evan walks in first and sits in the chair and right in front of him walks in his father, jason, who is super sleepy and is accompanied by a nurse and a guard and tells him not to bite evan because he seemed a little scared, he seems to be a very nice guy until suddenly evan wakes up from the trance and jason is on top of him hanging him, saying it's the only way, the guard knocks him out, taking him off evan, his mother enters desperate and protects evan although jason is already very bad, the blow was very forceful and he dies in front of evan...