Americans Ben and Sean (Max Minghella and Emile Hirsch) travel to Moscow to sell their social networking/party locating software. As they approach the airport the plane short circuits due to an electrical storm but regains power. They find their Swedish business partner, Skyler (Joel Kinnaman), has betrayed them and already made a deal with the Russians, using a knockoff application. They go to a nightclub and meet Natalie (Olivia Thirlby), an American, and her Australian friend Anne (Rachael Taylor). The lights go out in the club and everyone heads outside. There, they witness what appears to be an aurora. Balls of light fall from the sky and then fade away. When a policeman investigates he is disintegrated. The invisible entities begin hunting and disintegrating people, sending them into a panic.
Ben, Sean, Natalie, Anne, and now Skyler hide in the club’s storeroom for seven days. With most of their food gone, the group plans to go to the American Embassy. They find the city full of scorched cars and cinders, but empty of people, except for a wary old woman who warns them of “the ghosts”. Ben and Sean search for supplies in a police car near Red Square while the others hide in the nearby GUM department store shopping mall. While they are searching the car, a barking dog discovers and fatally confronts an alien, but the dog is disintegrated. Ben and Sean successfully hide under the car as the alien moves closer, causing the car’s lights and siren to turn on. The alien moves on and the men run to the mall. Sean realizes that light bulbs give the aliens away. The group takes shelter in one of the mall stores. Sean and Natalie go to look for clothes and almost run into an alien who can’t see them through a glass wall. Sean theorises that the aliens can only see their electrical charge, but not through glass.
The group finds the American Embassy gutted and lifeless. All except Skyler go to the roof to get an aerial view. They find a logbook telling them that the invasion is worldwide. They also find a radio broadcasting a message in Russian. They hear gunfire. Ben and Sean go to help Skylar, but he is killed. When the others go outside they see a light in a nearby apartment tower and go to investigate, bringing the radio they found. They find a young woman named Vika and a man named Sergei, an electrical engineer. Sergei has made his apartment into a giant Faraday cage that hides everyone from the aliens. He has also developed a microwave gun that weakens an alien’s force field, so that it can actually be seen and killed. Vika and Sergei translate the message, which says that a nuclear submarine K-152 Nerpa is waiting in the Moscow River to take survivors to safety.