One of Lucy's Starlight mice, the most adventurous one, decided to explore the house Lucy and Bill were visiting in Belgium. Lucy forgot to warn him about her friend Debbie's cat, Jolie.
Jolie obviously had never met such a brave little mouse before and wasn't quite sure where he had come from or why he was sharing her chair. I suppose Belgian mice are more hesitant to greet a cat face to face.
Within moments, however, Jolie recognized that a smart little mouse like this could make a good friend. Plus she found his American accent to be quite adorable.