Former star of the NBC sitcom Wings Tim Daly is set to appear in the two-hour episode of Grey’s Anatomy that will serve as a pilot for the possible spin-off starring Kate Walsh.

The story line for the two-hour episode, being written by “Grey’s” creator/executive producer Shonda Rhimes, is being kept under wraps, but it is understood that it will feature popular “Grey’s” character Addison Montgomery-Shepherd (Walsh) on the verge of leaving Seattle Grace, a scenario that will be triggered if ABC goes with the spinoff for next season.