In a recent conversation, Ladybug had jokingly suggested to Chat Noir that if Alya knew both of their identities they could contact each other through her. When Marinette shares this conversation with her best friend, Alya thinks it's an idea that they should consider for real. The final decision is left to Chat Noir, it's his identity after all. But he'll have plenty of opportunities to talk to Alya, since Ladybug has the flu, and she's filling in as Scarabella.