'Person of Interest' Season 3 fall finale 'Lethe' first look clip: Watch

"Person of Interest" heads into its fall finale with Tuesday's (Dec. 17) episode "Lethe." Following the death of Carter, the team has to regroup and prepare for a new threat from Vigilance while also responding to the numbers punched out by the Machine.

The above Zap2it exclusive clip from episode 11 "Lethe" teases the growing partnership between Root (Amy Acker) and Finch (Michael Emerson). Root asks Finch to bring her a book, "False Gods: Pseudepigrapha in the Modern Age," and reprimands him for taking recent stresses out on "her" -- i.e. the Machine -- by "ignoring her." Here it's Root who gives Finch the new number, and tells him that they need to work together.

It seems pretty clear that the Machine is prepping for an onslaught, but Finch doesn't seem to have the easiest time coming to terms with seeing Root as an ally. Whether she is exactly what she says she is hasn't been determined, but their dynamic together is interesting nonetheless.

"Person of Interest" airs Tuesdays on CBS at 10 p.m. ET, and returns from hiatus on Jan. 7.

Photo/Video credit: CBS