Sarah Chalke guest stars this week, as seen in ABC's Grey's Anatomy promo.

This time she won't be playing a member of the medical staff, though.

The Scrubs alumna will also take a turn for the dramatic as she portrays the mother of a child with a mysterious illness in a case that promises to be one of the ninth season's most riveting.

Meanwhile, Alex is forced into an unlikely position as he works with Jo's boyfriend, and there's the usual chaos taking over Grey Sloan Memorial, as we've pretty much come to expect.

Check out photos from "Can't Fight This Feeling" below ...