(CNN) -- The "Star Wars" universe keeps on expanding.
Details of the plot for 2016's "Star Wars: Rogue One" were revealed during a panel at Star Wars Celebration fan festival Sunday in Anaheim, California.
Director Gareth Edwards ("Godzilla") showed an early teaser for the movie and revealed plot details for the "Star Wars" anthology film (the term Disney prefers instead of "spinoff"), starring Felicity Jones.
The movie will take place in between "Episode III: Revenge of the Sith" and "Episode IV: A New Hope" (known to many as the first "Star Wars" movie from 1977).
A group of rebels go on a rogue mission to steal plans for the Death Star. Jones will play a rebel soldier.
The movie won't begin shooting until this summer so the footage shown in the teaser -- including a glimpse of the Death Star -- won't necessarily appear in the finished product.
Edwards told the crowd that Jones is a "Star Wars" fan and dropped everything to take on the lead role.
Producer Kathleen Kennedy said "Rogue One" was one of the first pitches she received after becoming president of Lucasfilm in 2012, and she could not turn it down.
It was one of the final events at Celebration, where fans gather to talk about "Star Wars," dress in costumes, look for rare "Star Wars" merchandise and learn about future projects for the franchise.
The convention kicked off with the well-received trailer for this year's "The Force Awakens." Costumes and props from that movie also were on display. Anything bearing the movie logo was a hot item for collectors.
Tens of thousands are expected to have attended the event when all is said and done.
"Rogue One" is scheduled to hit theaters December 16, 2016.