Who plays Frank Matson, the serial killer in the Chicago PD finale?

Chicago PD has had serial killers on the brain during season 11. Most of the year has been spent in the pursuit of a man who has been terrorizing the greater Windy City under the nose of the IU. The team thought that the man may have been a police officer, based on a lead they got in the episode "Inventory," but it proved not to be the case.

Instead, the man, named Frank Matson, is a locksmith. He doesn't have police connections, but his job enables him to break into any home in the city and snatch/murder anybody he pleases. It's how he managed to evade capture for so long. "Inventory" finally confirmed his identity, but in doing so, it put Hank Voight (Jason Beghe) in a very dangerous situation.

Matson is played by actor Dennis Flanagan

Matson had Voight kidnapped, and unless the IU can find him in time, Matson is going to make sure that Voight never sees the light of day again. The stakes don't get much higher, so we felt it would be a good time to look at the serial killer and determine where we might have seen him before.

Frank Matson is played by an actor named Dennis Flanagan. If you are a fan of procedural dramas, the chances are good that you have seen Flanagan pop up for an episode here or there. He's been in Dick Wolf shows before, with a one-off appearance in a 2011 episode of Law & Order: SVU. He's also been a guest on FBI and the original Law & Order when it returned in 2023.

Flanagan has appeared on Chicago PD before

The most interesting aspect of Flanagan's career, however, is that Matson is the third character he's played in the One Chicago universe. It's the second character he's played in Chicago PD alone! The actor popped up in a single episode of the ill-fated Chicago Justice in 2017, and he played a man named Nick Morella in a Chicago PD episode from 2020.

That's right, he's been on PD as two men within the same decade! Morella was not a particularly strong character, whereas Frank Matson will go down as one of the most devious (and dangerous) foes in the history of the show. Talk about moving up.