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 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.
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.