The film opens in New York. People start to get confused in Central Park, repeating their words, standing still and sometimes walking backwards. We hear a few screams. A woman reading on a bench takes her silver chopstick-style hair pin out of her hair and stabs herself in the neck with it.
In the next shot, we see a science teacher named Elliot Moore (Mark Wahlberg), talking about the event science can not explain about thousands of disappearing bees, no bodies left, no trace. A student offers the opinion that this is a natural event that we will never fully understand. While speculating on the phenomenon that is the disappearing bees, Elliot is suddenly called out of class to a staff meeting warning about an apparent "terrorist attack" in New York in which terrorists have apparently released some kind of gas in Central Park, and advising that school is cancelled. As they leave, Elliot confesses to his friend Julian (John Leguizamo), a math teacher, that he and his wife are having some problems.
Eventually the movie moves on to show Rittenhouse Park where a cop on the road shoots himself in the head. A driver gets out of his car, takes the gun, and also shoots himself in the head. We see a pair of high heels walk over and a hand starts to pick up the gun, then a shot.
Meanwhile on a building site, workers on the ground are chatting when all of a sudden a body falls. Panicked, thinking the worker just fell off the roof by mistake, they rush over to his broken body (yes, this whole movie is very graphic and this scene shows his legs and arms with bones snapped from the fall into inpossible, bloodied positions). While over the body, another thud, another worker. They look at him confused; one is possible, two is unlikely, and when the third falls, it seems impossible. Then yet another and another, crashing to earth. When they look up they see many running off the edge, appearently by their own will, looking completely calm, and sure of their actions.
