As Finch's virus spreads, destroying both Samaritan and the Machine, Samaritan makes one last desperate attempt to preserve itself and the team undertakes one last mission to stop it... and not everyone will survive.

As Reese and Shaw race to catch up with Finch, he infiltrates a maximum-security government facility in a desperate mission which could mean the end for not only Samaritan, but for himself and The Machine as well.

The team must unravel a conspiracy and stay ahead of the Secret Service when the President of the United States becomes their newest POI. Also, Finch separates himself from the team and considers taking drastic action to combat Samaritan.

Finch's number comes up when a fatal error blows his cover identity and sets off a deadly series of escalating encounters with Samaritan's operatives.

The mysterious criminal mastermind known as "The Voice" returns and traps Reese and Fusco in their own precinct with several armed gang members and the latest POI. Also, Root makes a shocking discovery.

Reese and Finch become trapped in a hospital that becomes ground zero for a deadly viral outbreak. Also, Samaritan's newest recruit has second thoughts and Shaw continues to struggle with reality.

Root goes undercover at a radio station to protect the host of a conspiracy theory show who stumbles upon information that could get him killed. Also, Samaritan's agents try to convince a member of the team that their goals are noble.

The Machine sends Reese and Finch to a wedding to protect a pair of POIs before their nuptials. Also, Fusco becomes angry at being kept in the dark by the team and takes it upon himself to investigate a string of missing person reports.

Reese protects an NYPD analyst whose investigation into a software glitch has drawn the attention of Samaritan. Also, Reese and Fusco are threatened by an ally of Elias's, who is looking to avenge his friend's death.

Sameen escapes from Decima and reunites with the team, but is plagued by strange visions and searing headaches. She soon realizes that something is seriously wrong... and there's only one way out.

Past and present collide when the team's newest Number is investigating the death of his brother... who Reese killed when he worked for the CIA.

Finch and Root try to deal with the Machine's reboot, but it flags them--and Reese--as threats due to their violent histories. Meanwhile, Reese and Fusco try to deal with an escalating increase in Numbers... and not all of them are real.

It's a race against time as Reese and Finch try to get the dying Machine to the subway station so that they can decompress it to a server capable of holding its memory. Meanwhile, Root turns to an old friend for identity papers as Decima agents close in on her, and Fusco deals with IAB in the aftermath of Dominic and Elias's deaths.