"'If your father has the tickets--' I began, but was interrupted by the guard, who snapped:

"'Monsieur will give himself the trouble to remember that I do not understand English.'

"'Keep quiet!' I said, sharply, in French. 'I am not speaking to you.'

"The guard stared stupidly at me, then, at my luggage, and finally, entering the car, knelt down and peered under the seats. Presently he got up, very red in the face, and went out slamming the door. He had not paid the slightest attention to Wilhelmina, but I distinctly heard him say, 'Only Englishmen and idiots talk to themselves!'

"'Wilhelmina,' I faltered, 'do you mean to say that that guard could not see you?'

"She began to look so serious again that I merely added, 'Never mind, I don't care whether you are invisible or not, dearest.'

"'I am not invisible to you,' she said; 'why should you care?'

"A great noise of bells and whistles drowned our voices, and, amid the whirring of switch-bells, the hissing of steam, and the cries of 'Paris! All out!' our train glided into the station.

"It was the professor who opened the door of our carriage. There he stood, calmly adjusting his yellow night-cap and drawing his dressing-gown closer with the corded ta.s.sels.

"'Where have you been?' I asked.

"'On the engine.'

"'_In_ the engine, I suppose you mean,' I said.

"'No, I don't; I mean _on_ the engine--on the pilot. It was very refreshing. Where are we going now?'

"'Do you know Paris?' asked Wilhelmina, turning to me.

"'Yes. I think your father had better take you to the Hotel Normandie on the Rue de l'ech.e.l.le--'

"'But you must stay there, too!'

"'Of course--if you wish--'

"She laughed nervously.

"'Don't you see that my father and I could not take rooms--now? You must engage three rooms for yourself.'

"'Why?' I asked, stupidly.

"'Oh, dear--why, because we are invisible.'

"I tried to repress a shudder. The professor gave Wilhelmina his arm, and, as I studied his ensemble, I thanked Heaven that he was invisible.

"At the gate of the station I hailed a four-seated cab, and we rattled away through the stony streets, brilliant with gas-jets, and in a few moments rolled smoothly across the Avenue de l'Opera, turned into the Rue de l'ech.e.l.le, and stopped. A bright little page, all over b.u.t.tons, came out, took my luggage, and preceded us into the hallway.

"I, with Wilhelmina on my arm and the professor shuffling along beside me, walked over to the desk.

"'Room?' said the clerk. 'We have a very desirable room on the second, fronting the Rue St. Honore--'

"'But we--that is, I want three rooms--three separate rooms!' I said.

"The clerk scratched his chin. 'Monsieur is expecting friends?'

"'Say yes,' whispered Wilhelmina, with a suspicion of laughter in her voice.

"'Yes,' I repeated, feebly.

"'Gentlemen, of course?' said the clerk, looking at me narrowly.

"'One lady.'

"'Married, of course?'

"'What's that to you?' I said, sharply. 'What do you mean by speaking to us--'

"'Us!'

"'I mean to me,' I said, badly rattled; 'give me the rooms and let me get to bed, will you?'

"'Monsieur will remember,' said the clerk, coldly, 'that this is an old and respectable hotel.'

"'I know it,' I said, smothering my rage.

"The clerk eyed me suspiciously.

"'Front!' he called, with irritating deliberation. 'Show this gentleman to apartment ten.'

"'How many rooms are there!' I demanded.

"'Three sleeping-rooms and a parlor.'

"'I will take it,' I said, with composure.

"'On probation,' muttered the clerk, insolently.

"Swallowing the insult, I followed the bell-boy up the stairs, keeping between him and Wilhelmina, for I dreaded to see him walk through her as if she were thin air. A trim maid rose to meet us and conducted us through a hallway into a large apartment. She threw open all the bedroom-doors and said, 'Will monsieur have the goodness to choose?'

"'Which will you take,' I began, turning to Wilhelmina.

"'I? Monsieur!' cried the startled maid.

"That completely upset me. 'Here,' I muttered, slipping some silver into her hand; 'now, for the love of Heaven, run away!'

"When she had vanished with a doubtful 'Merci, monsieur!' I handed the professor the keys and asked him to settle the thing with Wilhelmina.

"Wilhelmina took the corner room, the professor rambled into the next one, and I said good-night and crept wearily into my own chamber. I sat down and tried to think. A great feeling of fatigue weighted my spirits.

"'I can think better with my clothes off,' I said, and slipped the coat from my shoulders. How tired I was! 'I can think better in bed,'