Prime Time television, and network television in particular, relies heavily on formula. Person of Interest has a simply one: every week, John Reese and Harold Finch get a number from a machine and have to figure out who they need to help and how. It’s a formula that could easily grow old, but after the better part of two seasons, Person of Interest still remains fresh.

Part of this comes from the fact that the show has built an intriguing mythology in the time it’s been on. In some ways, it’s the closest thing we have to a Batman T.V. show, complete with its own Rogues Gallery of recurring characters. The other part stems from the creative ways they continue to subvert the basic premise.

This week sees the most interesting variation on the concept so far, with Reese arriving too late to save his mark. By the time he is able to figure out what is wrong, the doctor he’s been sent to help is already doomed from polonium poisoning. He then teams up with the dying doctor to find his killer. The answer is less than earth shattering, but the plot is well told, if a little by the numbers. It resolves well, and in the mean time we get a couple of great scenes, one involving Warehouse 13’s Allison Scagliotti, who plays the doctor’s estranged daughter. It’s a short scene that plays out much like you’d expect it to, but it’s well acted and believable. The writers of the show had the decency to put doctor’s final face to face with his daughter near the beginning of the story, rather than subjecting the audience to a long, drawn out and unnecessarily sentimental good bye. Even the short phone call he makes near the end is played straight, with him never telling her that there’s something wrong. The other great scene involves the climax of the story, which I won’t spoil. I’ll just say that it’s low key and opens up a moral can of worms with viewed against the other half of the episode. Speaking of which…

Paralleling the doctor’s tale of personal comeuppance is the tale of Lionel Fusco, one of the detectives in Finch’s pocket. We’ve known from the beginning that he was, once upon a time, a dirty cop, and his arc on the series has largely been about his search for some kind of self reconciliation. This week, we are given his origin story, a cop who begins by covering up for a fellow detective and quickly spirals out of control as he starts offing drug dealers.

This story is told in flashbacks against the story in the present involving an IAD investigation into Fusco’s past. It comes down to his partner, Carter (the other detective working with Finch and Reese), to help him out, despite her better judgment. This also causes a rift between Carter and the rest of the team, and it was pretty fun to see her extort help from Finch before following up on his lead.

The episode closes with a huge game changer where the meta-plot is concerned. Finch realizes that their being too late to help the people the machine gives them is becoming a too common occurrence, and it is revealed that a virus has infected the machine. What this means and how they deal with it will be an interesting arc to see as this season draws to a close.

Overall, ‘In Extremis’ was a solid, if largely uneventful episode. I should point out that Reese is largely in the periphery of the Doctor’s story, stepping in occasionally to do something badass, and I think it’s a testament to the show’s quality and the writers’ confidence that they don’t feel the need to constantly have the main character of the show doing something. That they regularly pull it off only makes it better.