Ever since Heart has become family with Tayo and his friends, Lani feels a little left out. One day, Heart receives a pretty siren as a gift from Hanna. Lani gets even more upset as Heart gets all the attention in the town. That evening, Heart's siren disappears! Where is it? All the little buses suspect Lani for it as she has been getting jealous at Heart. What do you guys think has happened to Heart's siren? Did Lani really take it?

Heart receives a cute siren as a gift from Hana. Lani, already envious of Heart, becomes even more upset when Heart gets all the attention from everyone. That evening, Heart's siren disappears! The little buses suspect Lani because of her jealousy for Heart.