OK, so maybe that was a slow start to the CW's four part "Heroes versus Aliens" crossover event. However, since Supergirl exists in a different universe than The Flash, Arrow, and Legends of Tomorrow, it makes sense that their portion of the crossover was the shortest. After Kara and her team battled the latest Project Cadmus threat, Barry and Cisco arrived on Supergirl from The Flash and it's all happening, finally.
The arrival of the two S.T.A.R. Labs vigilantes was teased at the beginning of the episode, when a breach was attempted in the middle of Thanksgiving dinner. Then, at the end of Monday's episode, Barry and Cisco arrived on Supergirl to ask for help with... something. We don't know what. Well, we kind of do. While the episode cut off, ending in a cliffhanger before Barry told Kara what they were up against, the official episode description for Supergirl states that "Barry Allen and Cisco Ramon seek Kara's help with an alien invasion on their Earth."
According to the description for Tuesday's episode of The Flash , these alien invaders are called "The Dominators." It actually seems like the scene we saw in National City will happen in the middle of the episode — the way that he Ant-Man post-credits scene happened in the middle of Captain America: Civil War. Have I lost everyone with the Marvel metaphor? Let's hope not.
They were only there for one scene, but that's a pretty typical ending for Supergirl. Often, the tension for the next episode is teased in the previous. I know that the length of Barry and Cisco's stay on Supergirl may have been a little disappointing, but I have a feeling that the four-night event is going to make up for it.
Image: Bettina Strauss /The CW