Grace (Debra Messing) becomes chummy with her unpredictable neighbor Val (guest star Molly Shannon, NBC's "Saturday Night Live," who reprises a character she formerly played) from down the hall, and while the pair surprisingly find they share a mutual rapport, Grace's glow dims when she tells Will (Eric McCormack) that a sentimental music box has disappeared during her new pal's visit. Meanwhile, Jack (Sean Hayes) poses as a straight man to attend a party for former homosexuals who have become heterosexual - fully intent on swaying a new convert (Neil Patrick Harris, "Stark Raving Mad") back to his side of the gender-preference aisle. Megan Mullally also stars.