“I wonder how many rooms it has,” said his daughter.

“Not so many as you might expect, because I understand the whole first floor is planned for the girls’ social uses. A card room, several small rooms for the girls to entertain callers, a library, a larger reception room for dancing, and the dining room are all part of the plan. But you’ll soon go all over the place and see for yourself.”

Mary Louise’s eyes sparkled.

“It is going to be thrilling, Dad!” she said.

“I hope you don’t run into any danger,” he remarked a little apprehensively. “The Philadelphia police will have your name on file—I saw to that—so the minute you call for help you can get it. And don’t hesitate to phone me long distance any time you need me. I’ll give you my list of addresses for the week. Don’t stop for expense—we can’t consider money in cases like this.”

Mary Louise nodded proudly. Never in her life had she been so happy. She walked along beside her father with her head high and her eyes shining. Her only misgiving, as they approached the hotel, was caused by her extreme youth. She hoped fervently that nobody would guess her age.

The hotel was an attractive place. Set back from the street by a small terrace, its trim brick walls and white-painted doorway and windows looked cozy and home-like. What a nice place to live, Mary Louise thought, if you weren’t lucky enough to have a home of your own!

How thankful she was that the place wasn’t gloomy and tumbledown like Dark Cedars, where she had made her first investigations as an amateur detective! Nobody would be telling her that ghosts haunted the walls of Stoddard House.

Her father opened the door for her, and she preceded him into the lobby. It was rather small, as lobbies go, with only one counter-desk, one lounge, and a couple of elevators, which you worked yourself, at the side. But doors opened out from the lobby on all sides, revealing glimpses of numerous attractive reception rooms beyond.

Mr. Gay nodded to the girl at the desk and inquired for Mrs. Hilliard. In a couple of minutes a stout middle-aged woman appeared and smiled pleasantly at him. He introduced Mary Louise.