TESTING RELATIONSHIPS / ALEXA CHUNG GUEST STARS - Feeling the pressure to make her first Waldorf Designs fashion show a success, Blair must rely on help from an unlikely source, but some unexpected scheming causes a scandal on the runway. Serena discovers that befriending Steven’s (guest star Barry Watson) daughter Sage (guest star Sofia Black-D’Elia) is trickier than she thought, especially when she is forced to put her issues with Blair aside to make Sage happy. Nate publishes Dan’s first serialized article causing a stir and producing a serious threat. Meanwhile, Chuck begins to look into the clue that Amira (guest star Andrea Gabriel) left behind, which may help uncover what Bart (guest star Robert John Burke) is hiding. Kelly Rutherford and Matthew Settle also star. Bart Wenrich directed the episode written by Natalie Krinsky.