Flash Supergirl crossover
The Flash and Supergirl crossover is happening at CBSThe CW/ CBS

The Flash and Supergirl crossover is happening at CBS and Grant Gustin has already wrapped up filming for the special episode in Los Angeles. Kara Danvers and Barry Allen will come together in Supergirl's episode 18 titled Worlds Finest.

According to a report in Just Jared, Grant Gustin has returned to Vancouver, Canada, after shooting The Flash and Supergirl crossover in LA. The special episode will feature a different timeline as the title World Finest does hints at The Flash and Supergirl being the finest in their respective worlds. The crossover will air on 28 March on CBS.

A leaked on-set image also reveals some intricate details about the main antagonist for the crossover. The picture shows Grant Gustin on a coffee run and Melissa Benoist in her Supergirl costume with some fans. But even further in the background we spotted a DC Comics villain — Silver Banshee.

Previously CBS officially revealed that Chasing Life actress Italia Ricci has been roped in to play DC Comics villain Silver Banshee in the CBS series. Executive producer Andrew Kreisberg said in a statement. "We are so excited to be working with Italia, We've been a fan of her work for years and we cannot wait to see her take on this iconic comic book role."

According to the network, Ricci is joining the cast of Supergirl as Siobhan Smythe, Cat Grant's latest hire who at first becomes a work nemesis for Kara. But she later proves to be a more deadly foe for Supergirl when she takes on the mantle of DC Comics villain Silver Banshee.

Barry from Central City will undertake a multi-universe journey to Kara Danvers's National City to help her fight the Silver Banshee. The promos and description for the episode is expected to be out soon.