Robert Manning Jr.

Reese and Finch attempts to rescue the Machine's source code before it deteriorates beyond repair. Root fights for her life against an onslaught of Samaritan's agents and Fusco is faced with hard questions following the deaths of Dominic and Elias.

As Decima uses Samaritan's feeds to hunt Reese and Shaw, Greer (recurring guest star JOHN NOLAN) exploits Finch's greatest weakness – by threatening his former fiancée and love of his life, Grace Hendricks (recurring guest star CARRIE PRESTON) – in an attempt to lure him out of hiding.

In the Season Four finale, Finch and Root race to save The Machine, which has been located by its AI rival, Samaritan. Also, Reese is caught in the middle of the final showdown between rival crime bosses Elias and Dominic.

Finch's number comes up when a fatal error blows his cover identity and sets off a series of escalating encounters with Samaritan's operatives, on the 100th episode.

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.