"Mystery Girl" is the first and second episodes of the third season of the television series The Naked Brothers Band, which premiered as a television movie on Nickelodeon on October 18, 2008[1] to 4 million viewers for children in the 6-11 and 9-14 age groups; it was the top rated episode of the series.
13-year-old Nat Wolff tries to grapple why Rosalina (Allie DiMeco), aged 15, is trying to get herself written out of the script.
To Nat's dismay, he later discovers that Rosalina is going to leave for a 6-month boat cruise around the world for winning a violin competition and he subsequently becomes mad at her.
Meanwhile, 10-year-old Alex Wolff panics when he finds out that he has to kiss his skateboarding buddy, Juanita (Teala Dunn), aged 11, for a scene in the film.
Nat finally accepts that Rosalina is leaving and decides to perform a serenade with the band for her, by singing his self-written composition, "Your Smile", outside of her apartment.