Rubidoux and Xela are stuck in 19th century Paris, with no way back home, and can't change shape to look like humans. When Rubi is picked up by the gendarmes, Xela escapes to the countryside and makes friends with a brave young boy. But soon be is bitten by a mad dog, and his only hope lies back in the city, in the medical laboratory of the famed Louis Pasteur. Can the scientist's pioneering work with germs and disease possibly help, or is Xela's new friend a goner himself? And where in the world, or out of it, can Rubi possibly be?