Plot summary
The Machine generates the number of watch repairman Lou Mitchell ( Ron McLarty ), who is consistently losing large sums of money at a casino. He and many other elderly gamblers are actually victims of a drug-money laundering operation headed by the casino's owner Dario Makris ( Michael Rispoli ). Finch breaks into the casino server room and gathers the needed evidence, but is caught and taken hostage along with Reese, Leon, and Lou. They are forced to play a game of Russian roulette, but Reese gets them out alive after Lou sneaks the bullet out before it enters the gun.
Meanwhile, HR incriminates Detective Szymanski ( Michael McGlone ) so the head of the Russian mob can be exonerated and give financial support to HR. Cal Beecher was the one who told IAB that Szymanski was corrupt, acting on information from one of Beecher's CIs. Carter succeeds in clearing Szymanski, but he is later killed along with the ADA by HR boss Alonzo Quinn, who makes it look like an assassination by an outside figure. Detective Terney ( Al Sapienza ) of the homicide task force is revealed to be an HR operative, potentially watching Fusco and Carter.
Credits
Adapted from Wikipedia contributors, Person of Interest season 2. HTML formatting and reference markers removed.