Lionel is investigated in relation to Dominic's death. Away from Samaritan, Mr. Reese and Harold try to save the Machine. Root is on the run.

Root and Finch work on bringing Northern Lights back online. They are successful and thus they start receiving numbers from the irrelevant list. However, the Machine is not as productive as before.

Reese's cover could be blown when he realizes the latest POI has ties to his old CIA colleague, Kara Stanton.

Shaw escapes her captors, but the team is unsure of her mental state when she begins to act paranoid and reckless.

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.

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.

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.

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.

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.

Finch's number comes up when his cover identity is blown and sets off a deadly series of encounters with Samaritan's operatives.

Harold goes on a road trip with the Machine, while the rest of the team receive a new number; the president of the United States.

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 of the war with Samaritan.

Finch, Reese, Fusco and Shaw embark on one last mission to prevent Samaritan from destroying The Machine and cementing its hold over mankind.