In this episode of Supergirl, the villains for Crisis on Earth-X crossover come from a hellscape of dark skies and red lightning. A black-clad figure, familiar but masked, is wearing an SS armband when he takes out a group of rebels before killing a masked hero who turns out to be James Olsen.
Nazi-archer collects some sort of device that will let them reign forever. He delivers it, along with a Nazi salute, to an evil scientist, and a flying masked woman.
Oliver is fighting ninjas in Star City when Felicity confirms that they plan to attend.
Kara and Alex are spending some romantic time together when she decides that Alex is going to be her plus-one for the West/Allen wedding.
The next thing we know, Kara’s joined Iris, Caitlin, and Felicity for manicures and champagne. Iris asks Felicity if she and Oliver are next to the altar. “Maybe once the city’s not being attacked and Oliver’s no longer under indictment and he’s spent enough time with his son who’s still mourning the loss of his mother,” Felicity replies.
Meanwhile, Barry’s trying on his penguin suit and worrying about his vows. Oliver enters in his own tux. Oliver assures him that the vows will come, and Barry asks Iris’ question: When will Oliver and Felicity tie the knot?
Oliver assures Barry that he loves Felicity but with everything going on, it’s not the right time. Still, Barry’s pleased that Oliver’s finally learned that being a superhero doesn’t exclude loving someone. In fact, it gives you something to fight for.
Stein tinkers with the serum and comes up with a way to end Firestorm but still leave Jax a superpower. Jax isn’t impressed at the thought of becoming the Spectacular Sticky Man. The extra time in the lab does allow Stein and Caitlin a chance to talk about Ronnie, and Stein vows that once he’s not Firestorm, he’ll be a better husband, father, and grandfather.
The rehearsal dinner, which is held at Jitters is lovely. Over shots of booze, Alex tells Sara about the end of her engagement, and they toast to how awful it is to be at the rehearsal dinner for the world’s most perfect couple.
Barry finds Kara looking down on the proceedings from the second story. She briefly explains the Mon-El situation and says it’s her own fault for trying to live as something other than Supergirl. She’s different than Barry and Oliver, who can let love into their lives; she’s an alien, and she’s alone. Sensing defeat, Barry backs off of this topic and asks if Kara will lend her talents to the ceremony the next day. She agrees.
Then Joe delivers a toast commending the grace, trust, and love Barry and Iris have shown during their recent challenges. “Thank you for showing me how to love again,” he says, raising a glass to his children.
Inspired, Oliver suggests that he and Felicity do something along these lines: friends, family, crab cakes, toasts. And he doesn’t just mean a rehearsal dinner; he wants the wedding, too. Although he doesn’t go down on one knee because he’s sore from the ninja fight, he proposes beautifully to the love of his life.
Felicity says she doesn’t need a piece of paper to make things legal and suggests they discuss it some other time. Oliver replies, “I’m actually physically incapable of talking about anything else right now.” The conversation ends with her yelling, “Oliver, I don’t want to marry you!”
The ceremony gets underway when Kara steps to the front to sing as Iris and Joe come down the aisle. Barry’s eyes shine with tears. The minister steps up to begin the ceremony, but when he reaches the “speak now” portion, he’s swiftly vaporized. The fatal blast was courtesy of Nazi-girl, who growls, “Peace is overrated.”
Barry and Wally speed around to catch bullets, Firestorm appears, Kara whips off her glasses, Cisco encourages Caitlin to channel her frosty roommate and Mick grabs his heat gun.
Thankfully, Oliver brought along his wedding bow and is able to deflect a Nazi arrow headed toward Harrison, who’s evacuating the humans. Then he has Cisco breach him up to the balcony to engage the Nazi-archer upstairs.
Nazi-Prometheus arrives on the scene. Sara and Alex team up to take him down, exchanging high fives when they do. Meanwhile, Supergirl’s taken to the sky to fight the masked woman. Supergirl delivers a super clap that stuns Nazi-girl, allowing Kara to punch her in the stomach. Nazi-girl falls, cradling her abdomen, and the Nazi archer immediately leaps over the railing to swoop her up, shouting for his troops to fall back.
At S.T.A.R. Labs, Barry promises Iris that he is going to marry her, while around them, Cisco’s down with a concussion, Stein marvels over Caitlin’s frosty dual nature, Sara and Jax march Nazi-Prometheus into a cell, and Mick announces that he successfully memory wiped all the wedding guests, so everybody’s secret identities are safe.
On a rooftop elsewhere in the city, Nazi-archer and Nazi-girl are joined by Nazi-Reverse Flash, who takes off his mask to reveal Harrison Wells. He yells at the duo for attacking before they were ready, but Nazi-archer argues that the wedding was too good to pass up. Then the pair remove their masks to reveal the faces of Oliver Queen and Kara Danvers. Nazi-Kara vows that they’ll have another chance to achieve victory, and when they do, they’ll kill every last one of our heroes.