Mr. Finch (Michael Emerson), a mysterious billionaire, developed a computer program for the government that predicts terrorist threats to the US. It was designed as a means to prevent another 9/11-type disaster, but Finch discovered that it was also predicting many "irrelevant" (non-terrorist) crimes. The non-terrorist data is dumped to a separate database and deleted each night. Finch realized that a great many domestic crimes could also be prevented if that data could be used. Finch built a backdoor into the machine that allows him to retrieve a list of Social Security numbers of people who will be involved in those crimes in order of occurrence. Unable to investigate the data on his own, Finch hires John Reese (Jim Caviezel), a former Green Beret and CIA field officer who is presumed dead, to help stop the crimes from taking place. The world thinks that Finch, like Reese, is dead. Finch made the choice of only transmitting the Social Security Numbers of the persons of interest so that if the backdoor is discovered, the government would have no clue as to what the numbers mean or that Finch is still alive.

Mysteries abound on the first season of LOST as the survivors of Oceanic Air flight 815 find themselves stranded on an unidentified island with little hope of rescue.