MARY-Kate Olsen, fresh off an appear ance on “Weeds,” will guest star on ABC’s “Samantha Who?”

Olsen will play a character whom Samantha (Christina Applegate) tries to “save,” according to eonline.com.

Olsen is scheduled to appear on only one episode of the ABC comedy this fall.

In the show, Applegate plays a woman who develops amnesia after a car accident and has to rediscover her life.

Olsen has guest starred on Showtime’s “Weeds” as Tara, a devoutly religious woman who’s romantically involved with Silas (Hunter Parrish), the son of series matriarch Nancy Botwin (Mary-Louise Parker).