The "Sound of Music Sing-Along" has come to town and no one is more excited than Grace. She plans for her and Will to attend the musical in character-like style by dressing up in costumes. However, her presumed-to-be fun night turns into a disaster when she ends up babysitting a group of children and Will accidentally goes to the wrong theater becoming further detained by James, a handsome man he meets. Meanwhile, Karen and Jack try to flee when she gets in trouble with the theater's manager, who blocks off the exits, trapping everyone inside and forcing them to plot their escape.

Grace is concerned and confused when Will so adamantly insists that she turn down her job offer from his former boss Margot, who has asked Grace to redecorate the law firm. When she takes the job after telling Will that she wouldn't, Grace learns some startling news that he has been hiding from her. Meanwhile, Jack discovers Karen's softer side when he finally sees what's inside the "forbidden room" at the Walker mansion.