Les Chats du Louvre, Tome 1

The sister of Marcel, the night watchman, vanished fifty years ago in the Musée du Louvre, and Marcel suspects that his sister found a way to disappear into a painting.

Cecile works as a docent at the Louvre, but she is dissatisfied with her job.

Marcel enlists Cecile to help him find his missing sister.

There are also cats who change back and forth into humans and one of the cats is intent on killing a small white cat. There's a painting restorer who is drawn into the story of the missing sister and talking paintings and even a strangely philosophical spider.

A completely original story with a large number of characters who are not very happy living on earth.

This was strange but ultimately sweet. I liked the cats much more when they looked like cats and not Cats the Musical style humanoid cats but that's just me! :)