"Person of Interest" was chockfull of genuine surprises and introduced a real shift in the dynamic of the series. [SPOILER ALERT]
No longer flush with unlimited financial resources and the powerful MACHINE at his side, Finch and Co. are on the run with new identities designed the shield them from Decima's new supercomputer in town, Samaritan. Compounding the drama, Decim-aritan is now backed by the US government that always coveted the power that Harold so carefully guarded from abuse.
And BIG SHOCKER, Vigilance was a puppet controlled by Decima all along! They created a terrorist threat SPECIFICALLY to strong arm the Senator into turning the "feeds" over to Decima. That threat was the destruction of the abandoned post office where the "Vigilance trial" took place. Poor Mr. Collier thought he was avenging the wrongful death of his brother, when he was being played as a patsy all along. OOOPS. Oh, and those 12 million viewers who were hanging on every revelation??? Shadows generated by Decima. No one saw Harold's testimony after all.
Only two recurring characters got their tickets punched in the season finale: Collier and Control's pack dog (naturally, dozens of beshadowed "red shirts" bought it too).
Root, Shaw, Finch, Reese and Fusco all make it out unscathed. Reese got over Carter's death pretty quickly IMHO and it looks like Fusco is done with. There can't be anymore NYPD antics with all the leads scattered to the four winds.
Sooooo... our team is divided, Decim-aritan is poised to rule the world and the MACHINE is only whispering to Root now. There's new passports and a half stack of hundreds keeping our pals from sudden death (except that Samaritan can't run outside of the U.S. and plenty of countries have less digital watch-dogging)... But who cares?
The tightly-wound Samaritan disciple (who apparently has legions of trench-coated thugs all too willing to turn their destinies over to a prettier version of Skynet) asked the new MACHINE what its commands for Decima were! WTF?!?! A blinking "Calculating Response" flickered across the screen as it faded to black.