But at that moment Blindway came strolling along, his nose in the air, his eyes fixed on the roofs of the houses outside the park, and he quietly dropped a twisted scrap of paper at his superior’s feet as he passed.  The chief picked it up, spread it out on the marble-topped table, and read its message aloud to his companions.

“City men say the informant is here and will indicate the men to be arrested in a few minutes.”

The chief tore the scrap of paper into minute shreds and dropped them on the grass.

“Things are almost at the crisis,” he murmured with a smile.  “It seems that we, gentlemen, are to play the part of spectators.  The next thing to turn up—­”

“Is Fullaway!” suddenly exclaimed Allerdyke, thrown off his guard and speaking aloud.  “And, by Gad!—­he’s got that man Chilverton with him.  This—­by the Lord Harry, he’s caught sight of us, too!”

Fullaway was coming quickly up the lawn from the direction of the Serpentine; he looked unusually alert, vigorous, and bustling; by his side, hurrying to keep pace with him, was the New York detective.  And Fullaway’s keen eyes, roving about, fell on Allerdyke and the chief and he made through the crowd in their direction, beckoning Chilverton to follow.

“Hullo—­hullo!” he exclaimed, clapping a hand on Allerdyke’s shoulder, nodding to the chief, and staring inquisitively at Appleyard.  “So you’re here, too, eh, Allerdyke?  It wasn’t you who sent me that mysterious message, was it?”

“What message?” growled Allerdyke.  “Be careful!  Don’t attract attention—­there are things going on here, I promise you!  Drop into that chair, man—­tell Chilverton to sit down.  What message are you talking about?”

Fullaway, quick to grasp the situation, sat down in a chair which Appleyard pulled forward and motioned his companion to follow his example.

“I got a queer message—­typewritten—­on a sheet of notepaper which bore no address, about an hour ago,” he said.  “It told me that if I came here, to this Hyde Park tea-house, at two o’clock, I’d have this confounded mystery explained.  No signature—­nothing to show who or where it came from.  So I set out.  And just as I was stepping into a taxi to come on here, I met Chilverton, so he came along with me.  What brings you, then?  Similar message, eh?  And what—­”

“Hush!” whispered Appleyard.  “Miss Slade’s coming out of the tea-house!  And who’s the man that’s with her?”

All five men glanced covertly over their shoulders at the open door of the tea-house, some twenty to thirty yards away.  Down its steps came Miss Slade, accompanied by a man whom none of them had ever seen before—­a well-built, light-complexioned, fair-haired man, certainly not an Englishman, but very evidently of Teutonic extraction, who was talking volubly to his companion and making free use of his hands to point or illustrate his conversation.  And when he saw this man, the chief turned quickly to Allerdyke and intercepted a look which Allerdyke was about to give him—­the same thought occurred to both.  Here was the man described by the hotel-keeper of Eastbourne Terrace and the shabby establishment away in the Docks!