She seemed not quite of the same world as that charming monsieur who was said to be going to marry her.

No; I was not attracted by Adele Rossignol." And when he had come to that point Hanaud looked up with a start.
"So the name was Adele," he whispered.
"Yes," said Ricardo.

"Helene Vauquier spoke the truth." Hanaud nodded with a queer smile upon his lips.
"Yes, there she spoke the truth.

I thought she did." "But she said Adele's hair was black," interposed Mr.Ricardo.
"Yes, there she didn't," said Hanaud drily, and his eyes dropped again to the paper.
"I knew her name was Adele, for often I have heard her servant calling her so, and without any 'Madame' in front of the name.

That is strange, is it not, to hear an elderly servant-woman calling after her mistress, 'Adele,' just simple 'Adele'?
It was that which made me think monsieur and madame were not of the same world.