From last night's episode of "Pretty Little Liars," viewers can tell that Ravenswood is no ordinary town. As the spinoff series prepares for its premiere, major casting changes have been made.

The Hollywood Reporter reports that actress Merritt Patterson, originally set to play the role of Tess, will replace Elizabeth Whitson as Olivia. Tess will be recast with a new actor.

"As we dug deeper into the mythology of 'Ravenswood' we decided to re-conceive the character of Olivia. Merritt Patterson seemed to be the best choice for the direction the character is now headed," say "Ravenswood" executive producers in a joint official statement.

While recasting is common prior to shooting, an actor swapping roles is somewhat rare.

"Ravenswood" is set to begin shooting in New Orleans next month, as "Pretty Little Liars" continues its fourth season.

In the episode "Under the Gun" last night, viewers caught a glimpse of Ravenswood, a gray, secular, anachronistic town that seems out of touch with time.

We meet two residents, Carla Grunwald (Meg Foster) and a mysterious gardener who remains unnamed. It's possible we will see both reprise their roles in "Ravenswood" once the show becomes its own entity.

"Ravenswood" will have its premiere this October as "Pretty Little Liars" continues into season five.