Rosie and Aglaée are finally moving into their first apartment. Just days before her 18th birthday, the YouTuber-turned-actress announces some big news that could change her life forever.

Rosie begins rehearsals with Timothée, and the experienced young actor isn't giving her a chance. On top of the stress of performing and her workload, Rosie is about to meet Océane, a mysterious girl who claims to be her half-sister.

Rosie discovers part of the truth about her biological father's life. In rehearsal, the pressure is at its peak, and a misunderstanding with Timothée creates irreparable turmoil. Fortunately, Rosie's entourage is there, but Océane's presence shakes hearts.

Aglaée discovers that Océane is keeping big secrets from Rosie. Forced to come up with a new line for her audition, Rosie cracks under the pressure. She decides to contact her biological father, which worries her mother greatly.

Torn over her life choices, Rosie fears for her future. Océane offers her a bold idea that could save her hearing.

Rehearsals resume, much to Rosie's delight. Océane confides in her and reveals her feelings for Jules. Rosie invites her to a family dinner. Tensions mount and the truth is revealed, bringing back old wounds.

It's the big day for Rosie, who's nervous before her audition. Simon is upset by a video, which worries Océane greatly. Rosie receives a call she wasn't expecting.

A surprise party is being planned at the apartment to celebrate Rosie's 18th birthday, but the surprises aren't what anyone expected. Emotions run high and secrets are revealed as Rosie's future hangs in the balance.