Revealing mistake: When Henry's mom is pushed off the cliff her cable is visible.
Visible crew/equipment: When Henry helps pull Mark onto the treehouse at the beginning of the film, if you look very closely to the left you can just make out a crew member dressed in black helping him on to the platform. The crew member then ducks back under the platform.
Revealing mistake: When Henry throws the dummy off the bridge, watch the rear window of the gray car; it explodes before being hit.
Visible crew/equipment: In the scene towards the end of the movie where the mother/aunt is holding onto Henry (Macaulay Culkin) and Mark (Elijah Wood), as they are dangling over the cliff, if you look closely at her holding onto Mark's hand, you can see a wire extending from under the sleeve of his coat to his aunt's.
Visible crew/equipment: When Henry pushes Susan off the cliff, look closely at her left side. You can see a wire attached to her hips when she falls.
Audio problem: When the kids are playing hide and go seek and Henry scares Connie, her scream is dubbed in too early. It happens before the shot changes so when you first hear her scream, her mouth isn't moving.
Continuity mistake: When Henry & Mark were chased by the dog, look carefully at the back of Henry's jeans and you will see a large dirt stain on it, but in the following scene over the cliff, there is a brief overhead shot over Henry and you will see that stain is gone.
Continuity mistake: When Henry attacks Connie for coming into his room and Mark steps in to stop him, they start fighting and Connie runs downstairs to tell on them. As the shot alternates back and forth, Henry's right hand jumps from Mark's ear to grabbing a handful of his hair and then back down again, but we don't see either boy move in a way that would explain the switch.
Revealing mistake: In the shot immediately following the multiple car collision, there are no people either in the cars or on the road.
Revealing mistake: After Henry falls dead on the rocks, a black cable is visible that is attached to the supposed corpse of henry and to another rock ground level, possibly to stop the dummy corpse from drifting away.
Answer: Henry apparently has what is called a "conduct disorder" - the term used for kids below the age of 18 engaging in what would be (and most likely will become) a diagnosis of sociopathy/psychopathy (antisocial personality disorder) when he becomes an adult. He is "evil", highly manipulative, self-centered, without remorse or other true feelings, and probably incapable of forming loving or long-term attachments. Many sociopaths are believed to have above average intelligence and make good imposters, capable of fooling others because they come across as "charming."
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