Orphan : 2009 Film

Synopsis (credits to wikipedia) :

Kate (Vera Farmiga) and John Coleman (Peter Sarsgaard) are experiencing strains in their marriage after Kate's third child was stillborn. The loss is particularly hard on Kate, who is still recovering from a drinking habit that cost her her job. They adopt Esther (Isabelle Fuhrman), a 9-year-old Russian girl they had met, from the local orphanage. While Kate and John's daughter Max (Aryana Engineer) embraces Esther almost immediately, their son Daniel (Jimmy Bennett) is somewhat less welcoming.

Kate grows suspicious when Esther, who watched Kate and John have sex, expresses far more knowledge of sex and its slang than would be expected for a child her age. Not long after Esther arrives, she pushes a schoolmate, who had picked on her, off a playground slide, breaking her ankle. Max saw Esther shove the girl, but covers for Esther by saying that the girl "slipped". However, Kate is further alarmed when Sister Abigail (CCH Pounder), the head of the orphanage, warns her and John about Esther's tendency to be around when things go wrong. Esther overhears this and later kills Sister Abigail with a hammer to the head. She forces Max to help her hide the body and the hammer. Daniel sees Esther and Max descending from his treehouse from behind a rock, not knowing they hid the hammer there. Later that night, Esther threatens to cut off Daniel's "hairless little prick before knows what it's used for" if he tells anyone what he saw.

Kate is told that the Russian orphanage Esther came from doesn't have any record of her ever being there. However, John does not believe her, despite continued ominous behavior by Esther. That night, Esther picks flowers for Kate that are from Kate's special plant and Kate pushes her to the ground. Later, Esther breaks her own arm in John's vise and convinces John that Kate broke it in the scuffle from earlier that day over the rosebush. On Esther's first day back at school, she slips Kate's SUV into neutral, nearly killing Max. Badly shaken, Kate buys two bottles of wine, but at the last minute pours one of them down the drain and leaves the other full.

Kate learns that Esther was housed at a mental institution in Estonia called the Saarne Institute, but when she expresses misgivings to John, he and her counselor think that Kate is relapsing into her drinking habit. After John produces the other bottle Kate bought the night before, he threatens to leave her unless she gets help.

Daniel learns of the hammer from Max and decides to get it and go to the police. However, Esther sets the treehouse on fire, intending to get rid of the evidence and kill Daniel. Daniel escapes by falling out of the tree, and gets a severe neck injury. Esther tries to finish him off by smashing a brick over his head, but Max shoves her out of the way just in time. Esther again tries to kill him at the hospital by smothering him with a pillow. As doctors rush to save Daniel, Kate angrily knocks Esther down for doing that and is sedated by doctors.

That night, Esther tries to seduce a drunk and sad John. John realizes Kate was telling the truth all along and threatens to call the orphanage. Esther, angry at being spurned, ransacks her room and later stabs John to death. Max witnesses this and hides in her laundry hamper.

As Kate is coming out of sedation, she gets a call from the Saarne Institute's director, Dr. Värava (Karel Roden), who reveals that Esther isn't a 9-year-old girl at all, but a 33-year-old woman named Leena Klammer. She has hypopituitarism, a disorder that stunted her physical growth, and has spent most of her life posing as a little girl. The doctor tells Kate that Esther is dangerously psychotic, and Kate should rush home to her family. Kate rushes home, where Esther shoots her in the arm before searching for Max.

Their chase takes them outside to a frozen pond, where Kate and Esther struggle before falling through a hole in the ice. Kate crawls out of the hole, followed by Esther, who begs for her life, addressing Kate as "Mommy". Kate angrily responds that she is not her mother and kicks Esther in the face, breaking her neck and sending her back into the pond to drown.