Colantoni plays school teacher Charlie Burton whose number is up, which gets Reese on the case. Charlie witnesses a mob shooting. The killers are intent on getting rid of Charlie, and Reese is determined to protect him. Early in the action, Charlie is shot in the shoulder and Reese's phone is knocked out of commission, which makes it much more difficult for Finch to oversee the operation (suggestion to Reese and Finch - work a few spare phones into standard procedures).
The soft-spoken Colantoni is perfect for the twist that awaits us concerning Charlie - who turns out to be not an innocent witness but Elias, head of the rival gang that's seeking to knock out the Russian mob in New York. Elias has been undercover as a teacher to get a better sense of the community, and build up grass roots support.
Reese realizes what's going on a little too late to stop Charlie/Elias, who walks away in Verbal Kint/Keyser Soze fashion. We'll no doubt be seeing more of Elias somewhere down the line in Person of Interest.
This is what I like most about the show - Finch and Reese are not infallible. There is always the possibility that the number that comes up is not a victim's but a villain's, and in episode 1.7 the bad guy was bad indeed.
The weakest part of the show continues to be the Detectives Carter and Fusco thread. It was worked into the story in 1.7 well enough, and will likely have some major impact before the end of the season, but at this point it's mostly a distraction from the major action.
See also Person of Interest of Interest ... Person of Interest 1.2: Reese and Finch ... Person of Interest 1.5: Potentials
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