Supergirl brings the “Elseworlds” crossover to its hopefully thrilling conclusion

Here’s what’s happening in the world of television for Tuesday, December 11. All times are Eastern.

Top pick

Supergirl (The CW, 8 p.m., special night, midseason finale): Once a year, The CW decides to take a whole bunch of its favorite superfriends and throw them into some big mess of trouble, all in service of telling a weird story that compels Supergirl fans to watch Arrow, and Arrow fans to watch The Flash, and fans of The Flash to watch those other shows… you get the idea. This year’s crossover, called “Elseworlds,” began when Oliver Queen (Stephen Amell) woke up as Barry Allen, and Barry Allen (Grant Gustin) woke up as Oliver Queen. Kara Danvers (Melissa Benoist) woke up as herself, thank the lord, and it’s with her series that “Elseworlds” ends. The CW is keeping things pretty close to the vest with this one—all we really know is that there will be some sort of climactic standoff, and that things are all still pretty topsy-turvy—but if the giddy energy of the first two segments continues, it’ll be a damn good time. Caroline Siede will throw on her tights and swoop in to recap the banter and the battles alike.

Regular coverage

Wild card

Letters From Baghdad (PBS, 9 p.m.): We admit that we don’t know much about Gertrude Bell, the British explorer, writer, and spy who is the focus of this PBS special. There was that Werner Herzog movie. There’s her lengthy Wikipedia page. That’s about it, sadly. But PBS, as it so often does, stands ready to correct this deficiency! It doesn’t involve superheroes (as far as we know) or anything particularly holly jolly, but any chance to learn about someone called “the female Lawrence Of Arabia” seems like one we should take.

And that was all true before we realized Tilda Swinton was playing Bell in voice-over.