“I don’t know how much romance and adventure there usually are in police proceedings,” replied Appleyard cautiously.

“A good answer, Mr. Appleyard,” said the chief laughing.  “Ah, there’s a lot more of both than civilians would think, in addition to all the sordid and dismal details.  What do I make out of it, Mr. Appleyard?  Why—­I think somebody has all this time been making a special investigation of this mystery for himself, and that at last he’s going to wind it up with a sensational revelation to—­us!  Don’t you be surprised if you’ve an application for that fifty thousand pound reward before to-night!”

“You really think that?” exclaimed Allerdyke incredulously.

“I shouldn’t be surprised,” answered the chief, “Something considerable is certainly at hand.  Now let us settle our plan of campaign.  This tea-garden, I remember, is a biggish place.  We will sit down at one of the tables—­we will appear to be three quiet gentlemen disposed to take a cup of coffee with our cigars or cigarettes—­we will be absorbed in our own conversation and company, but at the same time we will look about us.  Therefore, use your eyes, gentlemen, as much as you like—­but don’t appear to take any particular interest in anything you see, and don’t openly recognize any person you set eyes on.”

It was a very warm and summer-like day, and the lawns around the tea-house were filled with people, young and old.  Some were drinking tea, some coffee; some were indulging in iced drinks.  Nursemaids and children were much in evidence under the surrounding trees; waitresses were flitting about hither and thither:  there was nothing to suggest that this eminently London park scene was likely to prove the setting of the last act of a drama.

“You’re much more likely to see and to recognize than we are,” remarked Allerdyke, as the three gathered round a table on the edge of the crowd.  “For my part I see nothing but men, women, and children—­except that I also see Chettle, sitting across yonder with another man who’s no doubt one of your lot.”

“Just so,” assented the chief.  He gave an order for coffee to a passing waitress, lighted a cigar which Allerdyke offered him, and glanced round as if he were looking at nothing in particular.  “Just so.  Well, I see my own four men—­I also see at least six detectives who belong to the City police, and there may be more.  But I know those six personally.  They are spread about, all over the place, and I daresay that every man is very much on the stretch, innocent enough as he looks.”

“Six!” exclaimed Appleyard.  “And four of yours!  That looks as if they expected to have to tackle a small army!”

“You never know what you may have to tackle in affairs like this,” replied the chief.  “Nothing like having reserves in hand, you know.  Now let me give you a tip.  It is almost exactly two o’clock.  Never mind the people who are already here, gentlemen.  Keep your eyes open on any new-comers.  Look out—­quietly—­for folk who seem to drop in as casually as we do.  Look, for example, at those two well-dressed men who are coming across the sward there, swinging their sticks.  They—­”