Six days had gone by.

The funeral of the unfortunate Edward Craig had taken place, and locally the sensation caused by the tragic discovery had died down.

The weather was beautifully warm, the sea calm, and gradually a few holiday-makers were appearing in the streets; women in summer blouses, knitted golf coats and cotton skirts, with flannel-trousered men. They were of the class who are compelled to take their holidays early, before their employers; with them came delighted children carrying spades and buckets.

Fearing recognition by the notorious Frenchman, I was greatly handicapped, for I was compelled to remain in the hotel all day, and go forth only at night.

Frayne and his men had locked and sealed the rooms which had been occupied by old Gregory and Craig, and had returned to Norwich. In their place had come a plain-clothes man who, as far as I could gather, lounged about the corners of the streets, and chatted idly with the constables in uniform.

The plain-clothes man in our county constabulary system is not an overwhelming success. His only real use seems to be mostly that of a catcher of small boys who go out stealing fruit.

By dint of judicious inquiry, made by my manservant, Rayner, whom I had summoned from London, I had discovered something regarding the foreign gentleman, who had taken apartments in the Overstrand Road.

Rayner could always keep a secret. He was a fair-haired, bullet-headed chap of thirty-two whom I had found, eight years before the date of this story, wandering penniless in the streets of Constantinople. I had taken him into my service, and never once had occasion to regret having done so. He was a model of discretion, and to a man constantly travelling, like myself, a veritable treasure.

Sometimes upon my erratic journeys on the Continent I took him with me, at others he remained at home in my little flat off Berkeley Square. If I ever called upon him to make inquiries for me, to watch, or to follow a suspected person, he obeyed with an intelligence that would, I believe, have done credit to any member of that remarkable combination of brains—the Council of Seven, of New Scotland Yard.

Living an adventurous life, as he had done, his wits had been sharpened, and his perception had become as keen as that of any detective. Therefore, I had called upon him, under seal of secrecy, to assist me in the investigation of many a mystery.

Knowing his value, I had wired to him to come to Cromer. He arrived when I was out. First, he looked through my traps, folded my trousers and coats, arranged my shirts and ties in order with professional precision, and when I returned, entered my room, saying briefly—

"I'm here, sir."

I threw myself into a chair and told him all that had occurred—of course, under strictest secrecy.

Then I gave him minute instructions as to making inquiries of the servants at the house in the Overstrand Road. A servant can always get useful information from other servants, for there is a freemasonry among all who are employed in domestic capacities.

Therefore, it was with interest that I sat in my room, overlooking the sea, on the following day, and listened to Rayner's report.

In his straw hat, and well-cut grey tweed suit, my man made a very presentable appearance. It was the same suit in which he went out to Richmond with his "young lady" on Sundays.

"Well, sir," he said, standing by the window, "I've managed to get to know something. The gentleman is a Belgian doctor named Paul Arendt. He has the two best rooms in the house and is the only visitor staying there at present. They say he's a bit eccentric; goes out at all hours, but gives lots of money in tips. Seemingly, he's pretty rich."

"Has he had any visitors?" I asked quickly.

"One. Another foreigner. An Italian named Bertini, who rides a motor-cycle."

"Has he been there often?"

"He came last Monday afternoon—three days ago," my man replied.

"Anything else?"

"Well, sir, I managed to make friends with the maidservant, and then, on pretence of wanting apartments myself, got her to show me several rooms in the house in the absence of her mistress. Doctor Arendt was out, too, therefore I took the opportunity of looking around his bedroom. I'd given the girl a sovereign, so she didn't make any objection to my prying about a bit. Arendt is a rather suspicious character, isn't he, sir?" asked Rayner, looking at me curiously.

"That's for you to find out," I replied.

"Well, sir, I have found out," was his quick answer. "In the small top left-hand drawer of the chest of drawers in his room I found a small false moustache and some grease-paint; while in the right-hand drawer was a Browning revolver in a brown leather case, a bottle of strong ammonia, and a small steel tube, about an inch across, with an india-rubber bulb attached to one end."

"Ah!" I said. "I thought as much. You know what the ammonia and rubber ball are for, eh?"

The man grinned.

"Well, sir, I can guess," was his reply. "It's for blinding dogs—eh?"

"Exactly. We must keep a sharp eye upon that Belgian, Rayner."

"Yes, sir. I took the opportunity to have a chat with the maid about the recent affair on the East Cliff, and she told me she believed that the dead man and Doctor Arendt were friends."

"Friends!" I echoed, starting forward at his words.

"Yes, sir. The girl was not quite certain, but believes she saw the Belgian doctor and young Mr. Craig walking together over the golf-links one evening. It was her Sunday out and she was strolling that way just at dusk with her sweetheart."

"She is not quite positive, eh?" I asked.

"No, sir, not quite positive. She only thinks it was young Mr. Craig."

"Did Craig or Gregory ever go to that house while our friend has been there?"

"No, sir. She was quite positive on that point."

"What does the doctor do with himself all day?" I asked.

"Sits reading novels, or the French papers, greater part of the day. Sometimes he writes letters, but very seldom. According to the books I noticed in his room, he delights in stories of mystery and crime."

I smiled. Too well I knew the literary tastes of Jules Jeanjean, the man who was fearless, and being so, was eminently dangerous, and who was passing as a Belgian doctor. He, who had once distinguished himself by holding the whole of the forces of the Paris police at arms' length, and defying them—committing crimes under their very noses out of sheer anarchical bravado—was actually living there as a quiet, studious, steady-going man of literary tastes and refinement—Doctor Paul Arendt, of LiÈge, Belgium.

Ah! Some further evil was intended without a doubt. Yet so clever were Jeanjean's methods, and so entirely unsuspicious his actions, that I confess I failed to see what piece of chicanery was now in progress.

My next inquiry was in the direction of establishing the identity of the motor-cyclist.

That night Rayner kept watchful vigil instead of myself, for I had been up five nights in succession and required sleep. But though he waited near the house in the Overstrand Road from ten o'clock until four in the morning, nothing occurred. Jeanjean had evidently retired to rest and to sleep.

After that we took it in turns to watch, I having made it right with the night-porter of the hotel, for a pecuniary consideration, to take no notice of our going or coming.

For a whole week the notorious Frenchman did not emerge after he entered the house at dinner-time. I was sorely puzzled regarding the identity of that motor-cyclist. Would he return, or had he left the neighbourhood?

Early one morning Rayner, having taken his turn of watching, returned to say that Bertini, with his motor-cycle, had again met the "foreign gentleman" at the railway bridge—the same spot at which I had seen them meet.

They had remained about half an hour in conversation, after which the stranger had mounted and rode away again on the Norwich road, while Jeanjean had returned to his lodgings.

My mind was then made up. That same morning I took train to Norwich, where I hired a motor-car for a fortnight, and paying down a substantial deposit, drove the car—an open "forty," though a trifle old-fashioned—as far as Aylsham, a distance of ten miles, or half-way between Norwich and Cromer. There I put up at a small hotel, where I spent the rest of the day in idleness, and afterwards dined.

Aylsham is a sleepy little place, with nothing much to attract the visitor save its church and ancient houses. Therefore, I devoted myself to the newspapers until just before the hotel closed for the night.

Then I rang up Rayner on the telephone as I had made arrangement to do.

"That's me, sir," was his answer to my inquiry.

"Well," I asked, "anything fresh?"

"Yes, sir. A lady called to see you at seven o'clock—a young French lady. I saw her and explained that you were away until to-morrow, and——"

"Yes, yes!" I cried eagerly. "A French lady. Did she give her name?"

"No, sir. She only told me to tell you that if I mentioned the word 'nightingale,' you would know."

"The Nightingale!" I gasped, astounded. It was Lola! And she had called upon me!

"When is she coming back?" I demanded eagerly.

"She didn't say, sir—only told me to tell you how sorry she was that you were out. She had travelled a long way to see you."

"But didn't she say she'd call back?" I demanded, full of chagrin that I should have so unfortunately been absent.

"No, sir. She said she might be able to call sometime to-morrow afternoon, but was not at all certain."

I held the receiver in my trembling fingers in reflection. Nothing could be done. I had missed her—missed seeing Lola!

Surely my absence had been a great, and, perhaps, unredeemable misfortune.

"Very well," I said at last. "You know what to do to-night, Rayner?"

"Yes, sir."

"And I will be back in the morning."

"Very good, sir," responded my man, and I shut off. I paid my bill, went outside and lit up the big headlamps of the car. Then I drove slowly out of the yard, and out of the town, in the direction of Cromer.

It had been a close day, and the night, dark and oppressive, was overcast with a threatening storm. The dust swept up before me with every gust of wind as I went slowly along that high road which led towards the sea. I proceeded very leisurely, my thoughts full of my fair visitor.

Lola had called upon me! Why? Surely, after what had occurred, I could never have hoped for another visit from her.

Yes. It must be something of the greatest importance upon which she wished to consult me. Evidently she knew of my presence in Cromer—knew, possibly, of the efforts I was making to unravel the mystery of old Vernon Gregory.

Yet, I could only wait in impatience for the morrow. But would she return? That was the question.

The car was running well, but I had plenty of time. Therefore, after travelling five miles or so, I pulled up, took out my pipe and smoked.

I stopped my engine, and, in the silence of the night, strained my ears to catch the sound of an approaching motor-cycle. But I could hear nothing—only the distant rumble of thunder far northward across the sea.

By my watch I saw that it was nearly midnight. So I restarted my engine and went slowly along until I was within a couple of miles of Cromer, and could see the flashing of the lighthouse, and the lights of the town twinkling below. Then again I stopped and attended to my headlights, which were growing dim.

A mile and a half further on I knew that Rayner, down the dip of the hill, was lurking in the shadow. But my object in stationing myself there was to follow the mysterious cyclist, not when he went to keep his appointment, but when he left.

In order to avert suspicion, I presently turned the car round with its lights towards Norwich, but scarcely had I done so, and stopped the engine again, when I heard, in the darkness afar off, the throb of a motor-cycle approaching at a furious pace.

My lamps lit up the road, while, standing in the shadow bending as though attending to a tyre, my own form could not, I knew, be seen in the darkness.

On came the cyclist. Was it the man for whom I was watching?

He gave a blast on his horn as he rounded the corner, for he could no doubt see the reflection of my lamps from afar.

Then he passed me like a flash, but, in that instant as he came through the zone of light, I recognized his features.

It was Bertini, the mysterious friend of Jules Jeanjean.

I had but to await his return, and by waiting I should learn the truth.

I confess that my heart beat quickly as I watched his small red light disappear along the road.