Person of Interest Season 4 Trailer Teases Changed World, New Identities

“The world has changed,” declares… well, a mystery woman played by Cara Buono in the first trailer for Season 4 of CBS’ Person of Interest.

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The Mad Men alumna bookends the preview — which premiered at the San Diego Comic-Con — appearing in scenes with In Plain Sight‘s Fred Weller. But it’s the video’s meaty middle that you came for, a thrilling melange of Season 3 highlights plus plenty of brand-new footage, including Sam and Root lying low in a chic department store, Elias looking none too happy to see Reese again, and Root warning Harold that a war is at hand, “so pick a side.”

After all, she notes, their enemy has endless resources, while Team Machine has… actually, that’s a line best experienced first-hand. Listen for it.

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POI returns Tuesday, Sept. 23 at 10/9c.