In the One Chicago universe, the characters and plot lines on all four shows — Chicago Fire, Chicago P.D., Chicago Med and Chicago Justice — are all intertwined. But in real life, how well do the stars know what's going on on the other shows?

Turns out, not very well! During a recent set visit, quizzed actors and actresses from all four shows on their knowledge about their fictional One Chicago counterparts. And the results were, in a word, dismal. Hilariously dismal.

However, there was one exception! Chicago Fire's Kara Killmer is a self-proclaimed franchise fanatic.

"I'm embarrassed, but I'm also very proud," Killmer said, after nailing question after question about Med and P.D.

Exclusive: Go behind the scenes of the four-way One Chicago crossover

Unfortunately, Killmer's quiz partner and co-star Monica Raymund did not fare as well. Check out the video to see how some of the other stars did.

Chicago Fire airs Tuesdays at 10/9c on NBC. Chicago P.D. airs Wednesdays at 10/9c on NBC. Chicago Med airs Thursdays at 9/8c on NBC. Chicago Justice airs Sundays at 9/8c on NBC.