13. return 0

The Ice-9 virus begins to have disastrous effects globally. Samaritan has uploaded a copy of itself to servers in the Federal Reserve. Reese and Finch infect Samaritan's servers there with the virus, but Samaritan uploads a compressed version of itself to a satellite. The Machine tells Finch that the only way to defeat Samaritan is to upload a copy of the Machine to the satellite and that whatever building he uses for the upload will be destroyed by a cruise missile. At the subway, Fusco and Shaw are attacked by Samaritan agents led by Blackwell.

They escape on the Machine's train, capturing Blackwell. Blackwell stabs Fusco and escapes. Finch realizes he's on the wrong rooftop, having been tricked by Reese and the Machine. Reese tells Finch he plans to sacrifice himself, as saving one life can make a real difference depending on the person. A grieving Finch leaves as Reese holds off Samaritan agents. A week later, the world recovers from the virus and Shaw kills Blackwell to avenge Root. She meets with a recovering Fusco as the Machine's copy returns to Earth before contacting Shaw, while Finch returns to his former fiancée, Grace.