Chettle was hanging about the door of the warehouse when Allerdyke drove up.  His usually sly look was accentuated that morning, and as soon as Allerdyke stepped from his cab he drew him aside with a meaning gesture.

“A word or two before we go in, Mr. Allerdyke,” he said as they walked a few steps along the street.  “Look here, sir,” he went on in a whisper.  “I’ve been reflecting on things since I saw you last night.  Of course, I’m supposed to be in Hull, you know.  But I shall have to report myself at the Yard this morning—­can’t avoid that.  And I shall have to tell them why I came up.  Now, it’s here, Mr. Allerdyke—­how much or how little shall I tell ’em?  What I mean sir, is this—­do you want to keep any of this recently acquired knowledge to yourself?  Of course, if you do—­well, I needn’t tell any more there—­at headquarters—­than you wish me to tell.  I can easy make excuse for coming up.  And, of course, in that case—­”

“Well!” demanded Allerdyke impatiently.  “What then?”

Chettle gave him another look of suggestive meaning, and taking off his square felt hat, wiped his forehead with a big coloured handkerchief.

“Well, of course, Mr. Allerdyke,” he said insinuatingly.  “Of course, sir, I’m a poor man, and I’ve a rising family that I want to do my best for.  I could do with a substantial amount of that reward, you know, Mr. Allerdyke.  We’ve all a right to do the best we can for ourselves, sir.  And if you’re wanting to, follow this affair out on your own, sir, independent of the police—­eh?”

Allerdyke’s sense of duty arose in strong protest against this very palpable suggestion.  He shook his head.

“No—­no!” he said.  “That won’t do, Chettle.  You must do your duty to your superiors.  You’ll find that you’ll be all right.  If the police solve this affair, that reward’ll go to the police, and you’ll get your proper share.  No—­no underhand work.  You make your report in your ordinary way.  No more of that!”

“Aye, but do you understand, Mr. Allerdyke?” said the detective anxiously.  “Do you comprehend what it’ll mean.  You know very well that there’s a lot of red tape in our work—­they go a great deal by rule and precedent, as you might say.  Now, if I go to the Yard—­as I shall have to, as soon as you’ve done with me—­and tell the chief that I’ve found this photo of your cousin in Lydenberg’s watch, and that you’re certain that your cousin gave that particular photo to Mrs. Marlow, alias Miss Slade, do you know what’ll happen?”

“What?” asked Allerdyke.

“They’ll arrest her within half an hour,” answered Chettle.  “Dead certain!”

“Well?” said Allerdyke.  “And—­what then!”

“Why, it’ll probably upset the whole bag of tricks!” exclaimed Chettle.  “The thing’ll be spoiled before we’ve properly worked it out.  See?”

Allerdyke did see.  He had sufficient knowledge of police matters to know that Chettle was right, and that a too hasty step would probably ruin everything.  He turned towards the warehouse.