Marinette is a cheerleader, and although Adrien remains as wonderfully (frustratingly) oblivious as ever, there's something about seeing Marinette in action that makes things start to click in his mind. And his heart.

Marinette wins a trip with her friends but on the way there they end up staying in a mysterious mansion where they meet Felix. A charming young man who takes an interest in Marinette much to Adrien's jealousy. But not everything is what it seems. There is a murder Adrien must solve or he might lose Marinette forever.

Marinette finally confesses to Adrien, but he rejects her and the worst happens: she is akumatized! How will Adrien purify Marinette? What will happen after she is de-akumatized - will she even remember what had happened? And what about Hawkmoth, who had gotten a peek at Ladybug's mind? Will he change tactics now that he knows how the heroes have always stopped him?

Fed up with Chloe, Adrien does something he shouldn't. But, all actions have consequences.