Peter had gotten sucked into a portal while fighting a villian that wanted him gone. With that, he got transported to a different universe where he does not exsit there, where he's not in New York anymore but in Paris, and finds out that the heroes there are a cat like boy hero, and a ladybug like hero that fights like him. It may not be his universe, and it already has heroes of their own, but Peter is willing to help these two heroes and find a way back home to his universe. No matter how long it takes.
Cat Noir thought of helping his lady with guardian duties but it lead to an argument that he gives up on being her partner and that night he gets bitten by strange bats that turns him into a vampire. No longer human anymore, he leaves Paris and goes to Transylvania to start his undead new life. Ladybug realized how much he means to her as her partner, she now has to find him before Paris is doomed.