"We must try to find out, too." As the merry little party tramped upstairs to their rooms, Grace felt a hand on her shoulder.
"Do you really want to know who 'Peter Rabbit' was ?" whispered Elfreda.
"Yes," breathed Grace.
"Then don't tell the girls.

It was Kathleen." "Why didn't she unmask with the rest of us ?" demanded Grace, as they reached the head of the stairs.
"Why didn't she ?" repeated Elfreda.

"I'll tell you why.

She didn't wish any of us to know who she was.

Can't you see?
She wanted to be one of the crowd and she was afraid the girls wouldn't take kindly to her.