Undercover

[Luis Fok]

A chick that acts innocent but behind [closed] [doors] will [bang] anything.

[Justin Bieber]

(of a person or their activities) involved in or involving secret work within a community or organization, especially for the purposes of police investigation or espionage.

[Hina Muqadas]

working secretly using a false appearance in order to get information for the police or government: