Question: How can they use the elevator to get to the surface if the Red Queen shut the power down?
Answer: The force of the water moved the elevator up the shaft, hence why it did not go all the way up.
Question: In the openings scene, the prehuman drinks a tar-like fluid (like the one poisoning Halloway later on), while looking at a spaceship hovering above. He then dies, falls into the river and disintegrates. I do not understand this scene, is he the last of the surviving prehumans committing suicide and the ship above is the others leaving the planet?
Answer: The giant ship has landed on Earth to drop off the Engineer so that he can terraform the planet and make it sustainable for life. He might drinks the black stuff to break down his own structure and spread life on Earth through his own DNA.
Question: Who overrode the tunnel's explosion? Was it Marty since he had access to the system from the maintenance hatch?
Answer: It's stated that the tunnel should have blown hours ago, so the initial failure is most likely human error, that the order to blow the tunnel simply didn't get through to the demolition team on schedule. The subsequent problem blowing it up is referred to as being related to "a glitch up top", later stated as a "power re-route upstairs". While not stated outright, the only plausible explanation is that this was, as you rightly stated, due to Marty messing around with the equipment that he found in the hatch.
Question: Towards the end of the film, Heather steals the Seal from inside of Leonard, and we see him burn up. But the shot goes noticeably out of focus when this happens. What gives? The scene appears to be CG, so it makes no sense for it to go so badly out of focus. Were they just trying to cover up a dodgy effect?
Answer: I believe your theory is correct, it appears to go out of focus to help cover up some unconvincing CGI. The final explosion looks very cartoonish.
Question: At the end of the film it made it clear that there were not 2 siblings Ryan and Carrie Anne, there was just Carrie Anne that wanted to be a boy called Ryan, so why when Ellise picked up a photo frame did it have a young boy and young girl in the photo?
Answer: SPOILER ALERT: There actually were two siblings at one point, Ryan and Carrie Anne. The young Carrie Anne dies in a swing accident. In the end, we learn in flashback that the parents, who blamed Ryan for Carrie Anne's death, proceed to punish him by making him dress up as Carrie Anne and take her place. When he protests, he is physically abused by his mother. So, it isn't Carrie Anne who wanted to be a boy called Ryan. It is Ryan who was forced to take the role of his dead sister, Carrie Anne. Eventually, in the persona of Carrie Anne, Ryan kills his parents, and proceeds to find women whom he tries to transform into his dead sister.
Question: This is more of an observation than it is a question; however feel free to chime in with an answer. I realize that this is a "hidden footage" movie and each scene has to depict that. But Alex's actions at the end of the film seem to go against human logic. She finds her boyfriend dead in her closet, she knows her dad is across the street and that something is terribly wrong. Why would she take the time to find the video recorder, turn it on and take it with her to find her dad. Someone who just found a dead body in her closet would simply run out of the house or call the police; WITHOUT taking the time to worry about the camera.
Answer: Maybe seeing the dead body in the closet prompted her to grab her camera in case she needed evidence to show the police who had killed her boyfriend and possibly her father. There is enough time between shots that it is possible she calls the police from her cell while grabbing the camera.
Question: What's with all the baby corpses that Monica found in the hidden tunnels?
Answer: Early on, Ariel tells Monica that the old tunnels beneath the church are the burial site of many babies (the results of years of illicit sex between the nuns and priests), and that's what Monica comes across. It's possible the earthquake/aftershocks were meant to have exposed the tombs. The reason some of the bodies look bloody and more 'fresh' is most likely for shock value, typical of Eli Roth films.
Question: What exactly was Adam's plan the whole time? I don't fully understand it and even if I did, how does that make him the bad guy? Can someone please explain?
Answer: Adam wanted to turn the whole nation into vampires. And as head vampire, he would be the leader. Part of the plot line was vampires feed on slaves, so Adam wanted to keep slavery legal. During the course of the Civil War, Adam conspired with Jefferson Davis to send vampires to the front line to help with the war for the South, in return for claims to the North for his clan (although he would probably turn on the South afterwards).
Answer: She must have had trouble in keeping control of the elevator's power as the impact of the explosion blew out some of the windows and the sea came rushing in.
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