The story begins with Aya Brea, an NYPD rookie, attending an opera at Carnegie Hall with an unnamed date in New York City on Christmas Eve 1997. During the opera, everyone in the building spontaneously combusts, except for Aya, and an actress on stage named Melissa Pearce. Aya confronts Melissa onstage, and Melissa says that Aya’s mitochondria need more time to develop. She flees backstage, with Aya giving chase. Backstage, Melissa then mutates into a beast and flees into the sewers, declaring that her name is now Eve. The next day, on Christmas, Aya and her partner, Daniel, go to see a scientist at the Museum of Natural History named Dr. Klamp. He teaches the protagonists about mitochondria, but they do not find his information useful since it does not explain the previous nights events. Later that day, they hear that Eve is in Central Park, and to make matters worse, an audience has gathered at the park's theater intending to see a performance that Melissa Pearce was to give. Aya enters Central Park alone as Daniel is unable to pass through the entrance without spontaneously combusting. She makes it to the theater, but is too late to stop Eve, who causes the theater audience's mitochondria to rebel against their hosts and turns the crowd into a slimy orange mass. Aya chases after Eve and is knocked unconscious after a fight with her aboard a horse-drawn carriage. Daniel discovers that his son, Ben, was at the park, but had left the audience at the Central Park theater when he began to feel ill and when his mother began to act strange. He also learns that Manhattan is being evacuated due to the threat that Eve poses. Now it is up to you Aya to stop Eve from taking over the city and ultimately... The planet.