Today, I'm going to explain a german psychological thriller film called "Goodnight Mommy". Spoilers ahead! Watch out and take care!  

A family consists of a mommy and her two twins named Lukas and Elias. They have just moved to a new house in the middle of the forest and near a lake. 

Mommy used to be a choir member who was quite famous on local tv. One day, Lukas and Elias play hide and seek around their house. Realizing that their mother has returned home, the two immediately rush to meet their mother, but all they see is a woman with a bandage covering almost her entire face. That woman is their mother who had cosmetic facial surgery. This makes Lucas and Elias quite surprised but still obey her orders. But there is something strange going on. Mommy only gives her attention to Elias for no apparent reason. She provides food and drinks only to Elias, plays only with Elias, and only responds to Elias's words while Lucas is ignored. Because she is still in the healing stage, mommy also makes some new rules, such as the house must be in a state of complete silence. There should be no visitors, no animals, no bringing in things from outside, the house  curtains must always be closed and they are only allowed to play outside the house quietly.  

Seeing their mother's strange behaviour, the twins begin to suspect that beneath her bandages, their  mother may not be the same person. Mommy also acts cruelly and lashes out at Elias physically when he is naughty or disobedient. The boys comment that this is something their mother would never do. This makes Lucas and Elias even more convinced that mommy is not their mother because their mother would not scold them like that. In a dream that the twins seem to share, the boys' mother wanders into the woods in only her underwear. She disrobes completely, then unravels her bandages. Her head begins to spasm and spin. The next day, Lucas and Elias deliberately create troubles as a form of opposition. A fight breaks out, with the twins insisting they want their mommy back. Their mother thinks her children have lost their minds. When Elias asserts she's not his mom, Mommy punishes and forces him to say ten times that she's his real mother. She also tells him to stop talking to Lucas. Elias becomes very sad, knowing that mommy wants to separate the two of them. A few days have passed. Lucas and Elias still hate mommy and want their real mother to return soon. Later that day, mommy wants to meet them both; she states that she is not angry anymore. Mommy immediately enters the room with a new face that is not covered by bandages, but Lukas and Elias are still not sure that she is his mother, even after comparing her to the old photo of her mother. Mommy gives a boomerang as a form of apology for what has happened earlier. Elias immediately asks mommy's permission to play boomerang outside the house. As soon as mommy opens the back door, the kids run for their lives. 

They escape into town and eventually make their way to an old church and ask for the priest. The priest promises to drive them to the police station to report the impostor posing as their mother, but he tricks them and brings them right back home. The priest asks the mother to explain, but she just vaguely talks about how things have been difficult since the accident and the separation. Mommy returns inside but can't find Elias or Lukas anywhere. She eventually gives up and cries herself to sleep. That same night, Lucas and Elias do something to mommy. She wakes in the morning to the vision of her twins in their homemade goblin masks – and the realization she's bound to the bed. The twins have tied her down, making it impossible for her to escape. Just then, Lucas and Elias begin to inquire about the whereabouts of their real mother, she insists that she is their mother,  

Lucas and Elias begin to compare their real mother's photo with mommy. They have a fight because Elias has started to believe that mommy is their real mother , while Lucas is still convinced that mommy isn't their mother. When mommy is alone with Elias, mommy keeps trying to convince Elias that she is his real mother and tells Elias to let her free. Slowly, Elias starts to cut her feet loose, but is stopped when Lukas returns and asks what he's doing. He demonstrates that mommy's facial birthmark easily rubs off. Mommy tells them that they took it off in surgery; Elias doesn't believe it and slaps her.  

That moment, Lukas and Elias ask again about his mother's whereabouts while torturing mommy in very unnatural ways. The torture they do is extremely insane. Mommy is tied up on the bed for days. She wets her bed. The twins briefly set her free from her shackles to change the bedding. Mommy immediately uses this opportunity to escape. The twins, however, have set up a booby trap that causes her to fall, knocking her unconscious. The woman wakes glued to the living room floor. 

Elias starts to burn down the house to pressure her into telling them the truth about their mother. Mommy, in a final bid for her life, tells Elias she'll play along if he frees her. She'll pretend Lukas is alive again, make his breakfast – whatever he wants. Then, she tearfully explains to Elias that Lukas' death was not his fault and she begs her son to set her free, so they can both move on from the tragedy. Now, this is where everything is revealed! Lukas has been dead! Lukas has been merely a hallucination as a result of dissociative identity disorder, as Elias is incapable of accepting his other half's demise. Mommy initially plays along with Elias, acting as if Lukas was still around.  

For Elias, Lukas is real, but not for Mommy. Elias then challenges her to prove that she is their mother by telling him what Lukas is doing. Lukas is holding a torch near the curtain, but, obviously, the mother can't see that. Elias believes that his real mother could see Lukas. He takes then the torch from Lukas and sets the curtain aflame. The flames explode across the living room. Soon, it engulfs Mommy in flames. She dies a fiery death. 

The movie ends with the firefighters extinguishing the fire but arriving too late to save mommy.  The final shot of the film shows Elias and Lukas walking through the cornfield  and emerging to be with their mother, the three of them smiling and embracing.  And that's the ending of the movie "Goodnight Mommy".  

Now, for the explanation. The lady in the house is the real Mother. She is not an impersonator with devious intentions. A loving family in a beautiful home was destroyed because of a divorce and a son’s death. All Mommy is trying to do is get a fresh start, and she does this by getting plastic surgery. As part of the fresh start, Mommy also sold the old house and move to a different place. Mommy initially plays along with Elias, acting as if Lukas was still around. But she grows tired of this. It gets to a point where she even beats and threatens Elias to stop talking to his dead brother. Finally, at the end of the movie, we are shown this perfect family portrait dissolves into ashes. It’s clear this frame is an ironic representation of how it would have turned out without the accident that took Lukas’s life. Elias’s whereabouts after the fire remain a mystery.