With Finch missing – kidnapped by his hacker nemesis, Root, Reese enlists Detectives Carter and Fusco to get his friend back, Meanwhile, The Machine never sleeps, disseminating a new number to Reese.

The Machine gives Finch and Reese the number of a brilliant surgeon, but they soon discover that a resourceful third party has raised the stakes for this POI, forcing them to turn to an unlikely source for help.

A lethal government operative who tracks and stops terrorist threats before they occur finds herself on the run – and the new focus of Reese and Finch's attention. However, their pursuit proves to be their most formidable when they discover that her remarkable skill set equals their own.

Finch and Reese head to Atlantic City to protect the latest person of interest, an elderly gambler; Carter tries to clear another detective's name.