“Quite so, sir,” answered Chettle composedly.  “I want to draw your attention to some very special features and to ask you certain questions arising out of ’em.  We’ll take things in order, Mr. Allerdyke.  We’re driving now to the High Street—­I want to show you the exact spot where Lydenberg was shot dead.  After that we’ll go to the police-station and I’ll show you two or three little matters, and we’ll have a talk about them.  And now, before we get to the High Street, I may as well tell you that on examining Lydenberg’s body very little was found in the way of papers—­scarcely anything, and nothing connecting him with your cousin’s affair—­in fact, the police here say they never saw a foreign gentleman with less on him in that way.  But in the inside pocket of his overcoat there was a postcard, which had been posted here in Hull.  Here it is—­and you’ll see that it was the cause of taking him to the spot where he was shot.”

Chettle took from an old letter-case an innocent-looking postcard, on one corner of which was a stain.

“His blood,” he remarked laconically.  “He was shot clean through the heart.  Well, you see, it’s a mere line.”

Allerdyke took the card and looked at it with a mingled feeling of repulsion and fascination.  The writing on it was thin, angular, upright, and it suggested foreign origin.  And the communication was brief—­and unsigned—­

“High Street morning eleven sharp left-hand side old houses.”

“You don’t recognize that handwriting, of course, Mr. Allerdyke?” asked Chettle.  “Never seen it before, I suppose?”

“No!” replied Allerdyke.  “Never.  But I should say it’s a foreigner’s.”

“Very likely,” assented Chettle.  “Aye, well, sir, it lured the man to his death.  And now I’ll show you where he died, and how easy it was for the murderer to kill him and get away unobserved.”

He pulled the cab up at the corner of the High Street, and turned southward towards the river, looking round at his companion with one of his sly smiles.

“I daresay that you, being a Yorkshireman, Mr. Allerdyke, know all about this old street,” he remarked as they walked forward.  “I never saw it, never heard of it, until the other day, when I was sent down on this Lydenberg business, but it struck me at once.  I should think it’s one of the oldest streets left in England.”

“It is,” answered Allerdyke.  “I know it well enough, and I’ve seen it changed.  It used to be the street of the old Hull merchants—­they had their houses and warehouses all combined, with gardens at the back running down to the river Hull.  Queer old places there used to be in this street, I can tell you when I was a lad!—­of late years they’ve pulled a lot of property down that had got what you might call thoroughly worm-eaten—­oh, yes, the place isn’t half as ancient or picturesque as it was even twenty years ago!”