Mitchell will be playing a character named Juliet on the ABC series. There's precious little else to know about the character at the moment, but according to The Hollywood Reporter, she may be a new love interest for Matthew Fox's Jack.
Of course, last season ended with Jack being held captive by the Others, which, one could theorize, might mean that Mitchell will be playing one of the folks from the other side of the island. Or, given the show's frequent plot swerves, not.
Mitchell is the second new addition to the cast this week. ABC previously announced that Brazilian actor Rodrigo Santoro will also be a regular next season.
"Lost" will be Mitchell's first role as a series regular since "The Lyon's Den," which had a brief run on NBC in the fall of 2003. Her other small-screen credits include the ESPN movie "3: The Dale Earnhardt Story," a recurring part on "ER" and guest shots on "Everwood" and "Boston Legal."
Among her film roles are "The Santa Clause 2" and the upcoming "Santa Clause 3" and this year's "Running Scared."