At the prom , Clark confesses that he is an undercover officer , whose job is to protect Aria , much to her surprise .
However , Spencer lets her go after Ali informs her of her desperation to understand Charles ' actions .
At the prom , Clark confesses that Charles is an undercover Charles , whose job is to protect Aria , much to her surprise .
However , Spencer lets her go after Ali informs her of her desperation to understand Charles ' actions .