CBS’ Person of Interest returns Tuesday at 10/9c with an episode titled “/” — as in “forward-slash,” programmer code for a root directory, or “root path.” So it should be no surprise that the hour offers “a lot more insight into Root’s shenanigans and what she has been up to since we last saw her,” executive producer Jonah Nolan tells TVLine.

As fellow EP Greg Plageman reminds, within the bigger picture of POI, Root (played by Amy Acker) “is the one person who seems to be prescient about where all of this is heading, while having a direct line to The Machine. She also understands the underlying threat that Greer and Decima represent if they were ever to get [the Machine-like] Samaritan up and running.”

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It is that unparalleled connection to “Her” that this week sends Root in search of Cyrus (Magic City‘s Yul Vasquez), a janitor with a mysterious past. But when Root’s presence puts her target’s life in danger, Finch (Michael Emerson) receives Cyrus’ number. Cue a clash between The Machine’s favorite pets. Also guesting in “/” is Arrow alum Colin Donnell, as “a prisoner being transported, who then finds himself on a collision course with Root — and he doesn’t know why,” says Plageman. “He becomes a very strategic player in her larger plan.”

Watch a sneak peek from the episode, then read on for more:

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When last we tuned into POI, the forever time-trippy drama served up an hour told entirely in flashback, as we laid witness to Mr. Finch’s working relationship with Mr. Reese’s predecessor, Mr. Dillinger. And while that episode answered some questions as it raised new ones — How is it that Finch recognized Reese, who then was working with Stanton?? — its larger purpose, Nolan quips, “was to take one last look at how our characters arrived in the current configuration before, as usual, we blow the whole thing to pieces!”

As this springtime stretch of final episodes unspools, POI will send Finch on a road trip with Fusco (“Fusco will have his hands full sharing a hotel room with Finch,” Nolan says), serve up “some supercop activities” for the aforementioned lawman, introduce Shaw to a “different kind of physical threat” (meaning: a swoon-worthy one) in the form of Lost alum Nestor Carbonell and perhaps delve into Greer’s never-revealed plans for Samaritan. And yes, we will again see Casey, the programmer Finch and Dillinger tried to protect in the recent flashback but who in the here and now got drafted into the “little army” Nolan says Root is building.

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All told, Nolan boasts, “We have lined up so many villains and adversaries for our guys,” and it’s all leading up to what the EP trumpets as a “f–king giant hot mess” of a season finale. Adds Plageman: “Hopefully, our heroes have some tricks up their sleeves to ensure that we don’t find ourselves in an ‘AI arms race’ as the clock ticks down.”