In New York, there’s a skyscraper called the Millennium Building, which has 102 floors and 73 elevators. On the observatory deck, guards Andy and Gary are using the telescope to spy on the neighbor, who is having a very naughty party. As it starts to rain, the guards go back inside before some lightning causes the power to fail for a second.
While Andy goes to the bathroom, Gary notices his watch acting weird at the same time the elevator opens. As thunder continues to crash outside, Gary struggles with the elevator doors because they refuse to stay open. Suddenly Gary’s flashlight turns on by itself and when he tries to turn it off, the elevator doors shake along with his hand.
At that moment the doors close and Andy hears Gary scream, so he immediately goes back. He finds Gary holding a destroyed flashlight and blaming the elevator, which he is afraid of now. Andy thinks it’s nonsense and forces him to come along.
The next day, a group of pregnant women finish their yoga class and get in the elevator. They notice it’s going down faster than usual when suddenly the box sparks and stops. The guards hear the alarm and point out it’s the third time this week that this happens, but they never find anything wrong with the elevator.
In just a second the alarm shuts down and the guards assume the elevator is working again, so they don’t call maintenance. However the elevator is still stuck, and when the women try to press the emergency buttons or use the emergency phone, nothing happens. Their own phones have no signal either, so the women have to wait.
Eventually the guards get a call from another tenant saying the elevator isn’t working, which surprises them because the lights on their computer are fine. In the elevator, the women are starting to lose their patience because it’s getting too hot and hard to breathe. When maintenance finally arrives, the guards cut the power so the technicians can force the door open, but not even the key works.
Meanwhile the women activate a very loud alarm by accident and at least two of them start having contractions. In just a few minutes, all the women are feeling the contractions and one of them even starts giving birth. The maintenance team announces the doors are stuck so a guard arrives with an axe, desperate to help because one of the women is his wife.
A technician thinks it’s too dangerous and tries to stop him, so they end up fighting on the floor. At that moment the elevator starts going down really fast even though the power is still out. When the elevator makes it to the lobby, the guards run to open it and are shocked to find actual babies inside.
Meanwhile technicians Jeff and Mark stop at a diner to have breakfast and Mark calls out a rude man for mistreating the waitress. The man responds by punching Mark, throwing him at a table before leaving. Their breakfast is interrupted when they get a call from their boss telling them to go to the Millennium Building to fix the elevator.
At the same time reporter Jennifer is sent to the Millennium Building to cover the incident with the pregnant women, who are now being taken away in ambulances. Jennifer tries to ask the mothers some questions, but the cops forbid it. When Mark and Jeff arrive, they’re told about the elevator issues and manager Milligan wants them to get it fixed quickly because he’s afraid of getting sued.
Mark and Jeff are then taken to the engine room on the roof. While the duo checks the engine, they chat about a mechanic who recently self-deleted, which is strange because he’d seemed very happy. The guy thinks the engine may’ve been hit by lightning, but Jeff considers the idea ridiculous.
A few hours later, the duo is done checking everything yet couldn’t find anything wrong, so they just leave. In the meantime a blind man is at the hairdresser’s, who secretly gave him green hair. It turns out he uses being blind as an excuse to get too handsy with her, so this was her revenge.
When he and his guide dog get in the elevator, he chooses to go down yet the elevator starts going up. It doesn’t stop until floor 91, which is still under construction and currently empty, meaning nobody could’ve called it. The man presses a bunch of buttons but the elevator doesn’t work, so they come out.
The doors immediately close and the elevator goes down without them. The man calls for another elevator, which causes the dog to growl. The elevator goes up at great speed and when the screen announces floor 91 the doors open, but there’s no box.
The dog barks to warn his owner, who takes a step anyway and falls. He manages to hold onto the edge and the dog tries to pull him out, but the weight is too much and they both end up falling into the shaft. Later at night on floor 44, Andy and Gary are stealing some whiskey when they get a call from the security camera guys.
They explain an elevator is quickly going up but there isn’t supposed to be anybody in the building at this hour. Eventually the elevator stops and the doors open, but nobody comes out. Gary and Andy try to check on it, but Gary accidentally bumps against a statue and the noise causes the elevator to close the doors and leave.
The duo runs downstairs and finds the elevator open again on floor 40, but it closes as soon as they come closer. The little screen announces it’s going back to floor 44, yet when Gary’s flashlight starts malfunctioning, the doors open even though there is no box behind them. Andy takes a look inside and finds the dead guide dog hanging on a metal beam.
At that moment the doors close, capturing Andy by the neck. Gary tries to help him out but the doors are stuck. Suddenly the elevator box starts coming down and pushes Andy down until he gets decapitated against the edge.
The next day the Millennium Building closes all the elevators down, which leaves hundreds of tourists stranded outside. The press isn’t allowed inside and the cops refuse to share any information. Milligan has a meeting with the assigned detective, who explains they’ve checked the security cameras but they can’t find any intruders in the building.
Mark and Jeff are called to check on the elevators again, but Mark is going through a hangover and runs to the bathroom to throw up. Suddenly he’s found by Jennifer, who is pretending to be a cleaning lady but Mark can tell she’s a reporter. She takes a picture of him and asks him questions, but Mark refuses to answer.
When he leaves the bathroom Jennifer tries to follow him, only for the guards to kick her out. Afterward Mark and Jeff report to Milligan, telling him they didn’t find anything. With the detective’s support, Milligan announces they’ll open the elevators again.
The next day when Mark goes to work all his friends mock him because of something on the news. A confused Mark is called to his boss’ office, who is furious because the newspaper has printed Mark’s picture with a clickbait title. Jennifer quoted a sarcastic comment Mark made about elevators and now the police considers him a suspect too.
Mark is also shocked to learn he’s been assigned a new partner. When he looks out the window, he sees Jeff arguing with a scientist called Gunther. Mark asks his new partner about the mechanic that self-deleted and learns he used to be Jeff’s partner.
In the city, two friends are rollerskating everywhere, not caring about bumping into other people or cars. Eventually they make it into the parking lot of the Millennium Building, where one of the skaters is accidentally hit by a vehicle while the other one just keeps going. While the fallen man checks on his injuries, all the cars’ wipers start moving at the same time an elevator opens.
A very bright light sucks the man in and moments later it ejects him on floor 86. The body flies across the room, breaks a window, and goes through the fence to then fall off the building, dying as soon as it crashes to the ground. Seeing the incident on the news, Mark rushes to the Millennium Building but he’s not allowed to come inside.
On his way back, he sees Jennifer among the other reporters and follows her until she apologizes for her article. She shares some details about the incident, explaining that the police think the guy jumped to self-delete but she believes there may’ve been some foul play. On the lobby, a little girl manages to escape from the nursery and sits to play in front of the elevators.
Suddenly an elevator door opens and when the girl approaches it, it closes and a different elevator opens next. This goes on for a while and the girl has lots of fun running from one door to the other. When the elevator in the middle finally opens as well, the box goes up a few inches to leave a gap under it and the girl looks inside.
At that moment, the nursery teacher and Milligan hear her scream, so they run to the lobby to check. Thankfully the girl is fine, but her doll has been destroyed. When Milligan looks at the elevator, he finds a doll arm stuck in the door.
The night Mark is studying the elevator blueprints at home when he hears a noise outside and notices a shadow behind the door. He grabs a bat and opens the door only to find Jennifer, who has brought a video for him to watch. It’s a security recording showing the whole incident with the rollerskater, and Mark thinks this proves the guy self-deleted.
However Jennifer rewinds the tape to show him the timestamps: the elevator only took two seconds to go from the parking lot to floor 86, which should be impossible. Mark finally agrees something fishy is going on and brings Jennifer along to visit Jeff, who hasn’t been answering his phone. Jennifer asks him to watch the tape, only for Jeff to freak out and yell at them before leaving in the van.
This isn’t usual behavior, and when Jeff’s wife comes out of the house, she confirms Jeff hasn’t been himself lately. Jennifer and Mark leave and decide to have dinner together, during which Jennifer admits she thinks the elevator is haunted. After dinner, they go to Jennifer’s office and use her computer to search information on Gunther, since he’s the one who designs the elevators for the company.
He used to work for Kodelt industries, which was shut down after an investigation regarding bribery and illegal use of government money. Another article reveals the company used to work for the army making weapons. At that moment Jennifer’s coworker Chip walks by and notices the article they’re reading, so he shares what he knows.
Kodelt got in trouble for making biochips, which are computer chips based on live tissue. They built a computer base on dolphin brains that developed a mind of its own and the chips became able to reproduce themselves, so the whole computer grew and behaved like an actual living organism. However nobody knows what happened to it.
Chip never heard the name Gunther but he agrees to help them look for information. On their way home, Jennifer tells Mark she believes the elevator is haunted. The next day Milligan gets in the elevator and some blood drops fall on his shoulder.
When he looks up, he finds the hatch open. Suddenly the elevator stops and Jeff’s dead body falls through the hatch. A terrified Milligan crawls out but soon more employees see the body too.
Mark receives a call with the terrible news, so he and Jennifer rush to the press conference to get some details. To the duo’s shock, Gunther is sitting on the table with Milligan, the detective, and Mark’s boss. The detective explains Jeff had been a suspect and now they’re sure he was involved in all the incidents; he also claims that the police received a note from the murderer.
Mark can tell he’s lying but when Jennifer tries to ask Gunther about the biochips, he stops her because he thinks knowing that would make them look like suspects too. The duo leaves the building and Mark theorizes that the police are helping Milligan covering it all up. He also tells Jennifer about Jeff’s previous partner, saying he’s starting to think the self-deletion story had been a lie too.
They go to Jeff’s house to look for clues, but the police has already taken everything. Jeff's wife points out that he died the same way as his partner, which confirms the self-deletion story was a lie. Next Jennifer and Mark visit Jeff’s partner’s widow, but she won’t open the door so Jennifer picks the lock.
When the duo comes inside, they find a creepy altar dedicated to the dead guy. The widow finally agrees to talk and explains her husband was killed when they left him bleeding inside the building for three days. She thinks his spirit is still around and will only find peace when he gets his revenge.
At the Millennium Building, a large group of people get in the elevator, which starts going up very fast and doesn’t stop on any of the floors the tenants chose. Soon everyone starts crying or yelling in panic, and a child wets his pants. Suddenly the floor opens and a bunch of people fall to their deaths.
Some of them manage to hold on, but the elevator is going too fast and one by one they start falling too. The elevator never stops and eventually bursts through the roof, destroying half of the engine room. This time the incident reaches the White House and the president appears on a press conference saying all the elevator deaths were an act of terrorism.
At the same time the boss of the elevator company meets with Gunther and tells him that since he created this monster, now his responsibility is to kill it. Back to the Millennium Building, the police are showing up with more men than usual as part of an official operation. Jennifer arrives driving Jeff’s van while Mark hides in the back.
She pretends to be a company employee delivering elevator materials related to the investigation, but the cops still want to search the van. At that moment she gets a call from Chip, who tells her that biochips are still an ongoing project and now they’re using humans instead of animals. The police get tired of Jennifer buying time and force her to hang up before locking her up in a room.
Meanwhile Mark gets out of the van without being seen and enters the building by hiding underneath a police truck. While the cops keep bringing in boxes of ammo and explosives, Mark carefully sneaks around and uses his master key to open a service elevator, jumping on top of the box right before the cops use it to reach the last floor. Once the way is clear, Mark takes the stairs to the roof and dodges a few cops before entering the engine room.
There he uses his key again to activate one of the main elevators, which is seen by the guards on the main computer. After grabbing a lamp, Mark goes back to the last floor and rushes into the main elevator right before the cops could see him. At first it doesn’t move, but when Mark touches the hatch, the elevator immediately starts going down pretty quickly.
Using the buttons does nothing, so Mark forces a short on the elevator to finally make it stop. Next Mark climbs on top of the elevator box and uses the buttons there to control it. He goes up a few floors and makes the elevator stop when he notices a mysterious message on the wall written in blood.
Mark checks inside a hole and is startled when a bird flies out, but there’s nothing else so he starts going up with the elevator again. A few floors later, he finds a strange white substance on another hole and sparks on the cables above. When he tries going higher, the police make it to the engine room and deactivates the elevator, so now Mark has no choice but climb up using the cables.
He discovers a compartment in the wall and forces it open, which makes the box in the engine room shake and spark too. Inside the compartment he discovers the large glowing biochip and doesn’t hesitate to stab it multiple times. At the same time the elevator box in the engine room catches on fire and starts going down.
The biochip hasn’t died yet so Mark keeps on stabbing. The cops use explosives to blow the elevator door up and they start going inside, intending to capture Mark. The flaming elevator box is coming closer, so Mark moves out of the way to avoid death.
Most of the officers quickly get out but one of them trips and his legs are left hanging over the edge, so the elevator box splits his body in half on its way down. Mark gets ready to escape, but a second elevator goes up and causes some cables to tangle around his legs, so he’s dragged along. Using all his strength, Mark manages to untangle the cables and jumps off right before the elevator crashes against the engine room.
Debris starts falling and Mark has to hide under a beam to survive. Meanwhile Gunther arrives at the building and is allowed in because he has a special pass. The operation leader recognizes him on camera and realizes this isn’t related to terrorists.
While Jennifer gets into the vents to escape the room, Mark leaves the elevator and steals a weapon from the police boxes. Then he goes to floor 65 and opens the elevator door to find the biochip again. He gets ready to shoot only for Gunther to appear next to him with a gun.
Mark quickly disarms him and a fight ensues during which Gunther tries to kick Mark down the elevator shaft. Gunther almost wins the fight but it’s interrupted by Jennifer, who grabs the gun and forces Gunther to surrender. Mark uses the chance to grab the cop’s weapon again, but Gunther blocks the door to protect his precious creation.
At that moment the cops arrive and Gunther uses the distraction to capture Jennifer as a hostage. She bites his hand to free himself, and as soon as Gunther is alone, the elevator cables start moving like tentacles to grab him and drag him to his death. Mark’s leg ends up tangled in the process, so Jennifer throws him the weapon and he uses it to finally destroy the biochip.
The explosion sends Mark back into the corridor and the cables drop Gunther’s body. Sometime later Jennifer goes to pick up Mark at the hospital when he’s finally recovered. They get in the elevator and are startled when it suddenly stops, but it was Mark pressing the emergency button by accident.
Then he and Jennifer share a kiss. .
