Going to pick blackberries, Celestine discovers an old mill invaded by ivy. Ernest claims that the building is haunted, but far from scare Celestine, it sharpens his curiosity.
The mice prepare their annual party, to which Célestine is invited for the first time. Ernest is happy, but some other bears do not appreciate this party.
As soon as it freezes, Bears hibernate. Except Ernest, who claims to be used to extreme temperatures. When Celestine goes to look for flour at her friends' house, the blizzard begins to blow.
Ernest introduces Celestine to the stars and constellations. They all have animal names: there's the swan, the bear, the lion, but none of them mention mice.
Boléro is imprisoned by Jean-Mich and Jean-Lou, who take him for "The big bad bear". Fortunately, Ernest and Celestine will find the end of the story to save their friend.
Ernest's grandmother, Baboutchinka, visits Ernest. To surprise her, Ernest and Celestine want to reserve a table at the restaurant she knows well. But to dine in fancy places, you have to know good manners.
A new train, going directly to the sea, has just been inaugurated in the city. Celestine would like so much to go to the sea with Ernest, but the ticket is very expensive.
Mr. Martin, owner of the "Grandes Galeries", would like Ernest to play in his store. To accompany Ernest's violin, Mr. Martin lends him an old mechanical piano, completely out of tune.
More and more objects are disappearing in the city: Celestine's notebook, Bolero's hat, Madame Tulipe's binoculars - and even the Green Mouse cape. But what is going on here?
Ernest is honored to be asked by the mayor of the city to sing "The Song of the Bears". But his voice is causing problems, and who can replace him if not a big bear with husky-voice?
Augustin invites Celestine to celebrate her birthday. But, when will Celestine be able to celebrate hers? No one knows when she was born since Celestine was adopted.
Ernest and Celestine want to celebrate the New Year with a big party, but Mrs. Tulip complains about the noise. Celestine comes up with a plan to cheer her up.
Celestine prepares Mandarine's birthday drawings but has no more paint, and Ernest is hungry but penniless. However, they will have a meeting that will teach them many things about themselves and about others.
All the mouse children go to summer camp for the holidays, at "Les Souriceaux". Celestine would like to leave too, but she never went to the colony, and especially never left without Ernest.
Simeon, Celestine's penguin toy has disappeared. The whole town starts looking for the toy to console Celestine, who is sheepish. But what we're looking for is often right in front of our eyes.
