(Ben Claassen III/For Express) (Ben Claassen III/For Express)

In the opening scene of Monday night’s episode of NBC’s “The Blacklist” — which is set in D.C. — a character boarded a Red Line train. After a few minutes, he got up from his seat, abandoning his briefcase, and went for the exit. Just after the doors closed behind him, he pressed a button to release a deadly chemical weapon.

Awful, right? But what made me feel even worse about the situation was that I was laughing. If anyone thinks that set looked remotely like the D.C. Metro, they’ve obviously been hanging with the mayor of Toronto. Not only were the general aesthetics off, but even the details were conspicuously wrong. The sign on the train read “Farragut East-Express.” A completely comprehensible announcement recommended changing to the Yellow Line.

And, most bizarrely, the character was sucked into a conversation with a chatty fellow rider, who wanted to discuss her dad’s taste in hats. (By comparison, this is an actual exchange I had on the Green Line on Monday. Me, gesturing to a leather case: “Excuse me, but can I ask what that is?” Guy: “It’s a sword.” I got off at the next stop.)

“The Blacklist,” like nearly every other program set in this town, gets plenty of other stuff just as wrong. Later that episode, someone bought a house in what was labeled on-screen as “Tacoma Park, Md.” But it’s the transportation inaccuracy that bugs me, maybe because “The Blacklist” also stars actor Diego Klattenhoff. On “Homeland,” another D.C. show, he’s Mike Faber, who lives near the ubiquitous “Blue Route” bus.

I recognize that few television shows shoot in D.C., so crews have to improvise. (Although “House of Cards” managed to make the trip south from Baltimore for a very legit Metro scene.)

Still, I didn’t get upset over a flashback on “Scandal” that showed a character panhandling near a platform at Union Station. The brightly lit space and giant time displays were all wrong, but the dialogue — about track work and Red Line delays — helped me suspend disbelief.

So that’s my hint for other shows that insist on faking Metro scenes: Prove to locals that you know what’s up. One foolproof technique? Let our hero miss a connecting train and have to wait 20 minutes.