Desdemona died sometime in the night. Aunt Ada had had the cat since she was a tiny kitten, and she was naturally heartbroken. So was Boots, Desdemona's partner in crime and play and food and everything else that makes life worthwhile for two old cats.
Through her tears, Aunt Ada wondered if she could've noticed something or had done something differently that would have given Desdemona back to her for a while longer, but there just wasn't anything. The cat had looked good at bedtime, and was gone before the sun came up.