'Supergirl' Season 3 Finale Synopsis Released

The CW has relesed the official synopsis for "Battles Lost and Won," the June 18 season 3 finale to Supergirl.

The synopsis tells very little about what, exactly, will be happening in the episode, although it does certainly suggest that Supergirl returns to Earth after her decision to abandon it in favor of Argo City seen in the trailer for next week's episode.

The finale pits Supergirl and her team against Serena, the character played by iZombie veteran Anjali Jay.

In the most recent episode, Kara (Melissa Benoist) and Mon-El (Chris Wood) went to an asteroid in deep space looking for a black Kryptonian rock that they believe will allow them to reverse engineer a cure for Sam/Reign (Odette Annable.) However, when they arrive they discover that the asteroid is actually Argo, a populous city-state that survived Krypton's demise thanks to a protective dome. They also discover that Kara's mother Alura Zor-El (Erica Durance) is alive and well and that the black rock they seek is what is keeping Argo and all its residents alive.

As taking even a small part of the rock has consequences for the well-being of the Kryptonian survivors, Alura brings Kara before a council where she must plead her case for why they should give of one thing keeping them alive to save Earth. One of the members of the council? A woman named Selena and fans of Supergirl have seen her before -- as the hologram that instructed and aided Reign in her Fortress of Sanctuary.

However, that's not the only thing significant about Selena. If you thought that "Dark Side of the Moon" felt a little bit like the 1984 Supergirl movie, you're right. The plots are a bit similar to one another, though inverted, and Selena was a part of that film, too. You see, in the movie, Supergirl comes to Earth in search of an immensely powerful item called the Omegahedron -- an item that, incidentally, was mentioned on Supergirl in Season One -- that Argo City needs in order to survive. However, the Omegahedron was found by Selena, a power-hungry witch who intends to use the device to take over the world. Her wicked plot is ultimately thwarted and Supergirl takes the Omegahedron back to Argo and saves the day.

You can see the official synopsis below.

SHOCKING SEASON FINALE

Supergirl (Melissa Benoist) and team take on Serena in an epic battle for Earth.

Jesse Warn directed the episode written by Robert Rovner & Jessica Queller.