Tonight's episode of "The Flash" -- "Duet" -- was sweeping, romantic, and utterly perfect. This episode was full of everything a proper musical should have: love, revenge, mystery, and some amazing musical numbers. The cast of both "Supergirl" and "The Flash" shined in an episode that never once felt like a "musical gimmick" -- it only felt right. After putting Kara in a coma on "Supergirl," the Music Meister then came to Earth-1 and did the same thing to Barry. While Mon-El, J'onn, Joe, Cisco, HR, Iris, and Wally tried to rescue them, Barry and Kara found themselves trapped in a world inspired by 1940's Hollywood musicals. They had to sing, they had to dance, they had to do their best Ginger Rogers/Fred Astaire impressions to wake up from their own personal "La La Land." Inside the dream world, they quickly discovered the crux of the musical: to make sure that Iris and Mon-El got married -- wait, what? That's right, Barry and Kara had to assure the happiness of the two people they loved most in the world. After both couples' relationships suffered blows at the hands of Savitar and Mon-El's royal parents, the Meister sought to heal what was broken and show Barry and Kara what they needed most in the world. True love's kiss broke the spell (of course it did) and the episode ended on a truly happy note.

"She's Lost That Lovin' Feelin'"

"Duet" kicked off with Supergirl arriving on Earth-1 with Mon-El and J'onn J'onzz. Supergirl was in a coma-like state after being hit by Music Meister (guest star Darren Criss.) According to Mon-El and J'onn, Meister fled to Earth-1 after attacking Kara. Team Flash agreed to help Kara while Barry and Wally went after the Meister. Barry was hit by the Meister's powers too and he ended up in the same state as Kara. When Barry woke up, he was in a night club. The club was old fashioned and a young, blonde woman was singing on the stage. The woman was Kara and she was singing "Moon River," the song Audrey Hepburn made famous in "Breakfast at Tiffany's." Barry and Kara quickly realized they were trapped inside a musical since Barry had been binge-watching movies like "Singing in the Rain" since he and Iris broke up. When the Music Meister showed up inside their dream world, he explained the rules: follow the script, finish the musical, and don't die. Sounded pretty easy, right? Barry and Kara then watched as their sort-of friends Winn and Cisco performed an opening number in the club, Dolly Parton's "Put A Little Love in Your Heart" -- oh and the club was owned by Malcolm Merlyn, totally normal, right?

"Falling Slowly"

Everything seemed like it was going Barry and Kara's way until they realized the plot of the musical: they had to unite "Star-Crossed" lovers Iris and Mon-El. Barry and Kara were essentially inside the 1961 musical "West Side Story" -- Iris was Maria, Mon-El was Tony, and their fathers Malcolm Merlyn, Martin Stein, and Joe West were rival gang leaders. At some point someone should have broken into "When You're a Jet," but it never happened. What did happen was Barry and Kara both decided to let Iris and Mon-El get together and agreed to help them talk to their fathers. During this scene, John Barrowman, Victor Garber, and Jesse L. Martin got to sing the "Guys and Dolls" ballad "More I Cannot Wish You." It was beautiful, haunting, and highlighted the love that these fathers had for their children. This tender moment did not last, as both sets of fathers decided to go war. Before the war began, Barry and Kara did get to perform one musical number together -- "Super Friend" -- the totally enchanting original song written by "Crazy Ex-Girlfriend" creator and star Rachel Bloom.

"Tale as Old as Time"

Barry and Kara's "Super Friends" song was cut short when Merlyn, Stein, and West's rival gangs began to fire upon one another. Both Barry and Kara were shot and were unable to heal themselves because they had no powers in the dream world. Back in the real world, the Music Meister was parading around Central City with Barry and Kara's powers. Through a Vibe/Kid Flash/Martian Manhunter team-up, the Meister was brought down and put into the S.T.A.R. Labs pipeline. When Barry and Kara's bodies went into cardiac arrest from the gunshot wounds, Iris and Mon-El begged the Meister for help. His suggestion? Fight for Barry and Kara with their love. Mon-El and Iris then asked Cisco if he could Vibe them into the dream world, which worked. Iris and Mon-El both kissed Barry and Kara, which woke them up and broke the dream world spell. When the Meister appeared outside of the pipeline, he confessed that he was testing them the whole time to help them fall back in love with the ones they had pushed away.

"My Heart Will Go On"

The episode concluded with Music Meister zipping off to another dimension and Mon-El, J'onn, and Kara returning to Earth-38. Barry and Iris then went back to their apartment and Barry proposed the right way: by singing Iris the original love song "Runnin' Home to You." The song was written by the Academy Award-winning duo Benj Pasek and Justin Paul, who also wrote "City of Stars" for "La La Land." The song was powerful and perfectly captured Barry's feelings for Iris. As the song concluded, he got down on one knee, took out Iris' grandmother's ring, and proposed. Iris of course said yes and the episode concluded there. After last week's "I love you but I'm going to push you away" debacle, this was such a beautiful and heart-warming moment. We all know that Barry has been in love with Iris his entire life, why shouldn't he propose?

This episode was absolutely perfect and reunited two sets of lovers who let life and lies and Savitar get in the way of their happiness. It was a joy to hear everyone sing -- from Jesse L. Martin to Jeremy Jordan to Grant Gustin and Melissa Benoist. The song choices were amazing, the musical nods were appropriately chosen, and the original songs deserve to go Number 1 on iTunes. It's so amazing when a show like this can bring together some of the finest musical talent in Hollywood today. As it's been pointed out before, Gustin, Criss, and Benoist have been on "Glee," Martin has been on Broadway, Barrowman has starred in numerous musical productions -- you simply can't have a cast this talented and not do a musical episode. The writers, the cast, the musicians, the choreographers, and the director should all be proud -- "Duet" might be the best episode DCTV has ever done and the finest musical episode ever performed on television. Thank you, Greg Berlanti and co.

"Abracadabra"

Next week, "The Flash" heads back into the real world as Earth-19 villain Abra Kadabra shows up on Earth-1. This titular Rogues villain will be played by "Ant-Man" and "Gotham" star David Dastmalchian. Abra Kadabra will have important information for Barry on the identity and weaknesses of Savitar. Unfortunately working with Abra will put Barry against Gypsy and Caitlin will get caught in the crossfire.

DC COMICS’ CHARACTER ABRA KADABRA VISITS CENTRAL CITY – The Flash (Grant Gustin) battles Abra Kadabra (guest star David Dastmalchian), a villain from Earth-19, who makes him a tempting offer – release him and Abra Kadabra will reveal Savitar’s true identity. Desperate to save Iris (Candice Patton), Barry considers taking the deal but Gypsy (guest star Jessica Camacho) breaches in to capture the villain for her own reasons and during the melee, Abra Kadabra manages to escape. Barry is furious that Gypsy interfered but Gypsy refuses to back down, forcing Cisco (Carlos Valdes) to take sides. Meanwhile, Julian (Tom Felton) is still a bit cold towards Caitlin (Danielle Panabaker) but when she is severely injured in a battle with Gypsy, he rushes to her side. Nina Lopez-Corrado directed the episode with story by Andrew Kreisberg and teleplay by Brooke Roberts & David Kob. Original airdate 3/28/2017.

Airing Tuesdays at 8 p.m., “The Flash” stars Grant Gustin, Candice Patton, Danielle Panabaker, Carlos Valdes, Tom Cavanagh, Jesse L. Martin and Keiynan Lonsdale.