Through an oversight he forgets the key in the door, which he had placed in the outside before carrying off the body, intending when he returned to lock the door and carry the key away with him.
"Next morning you have the highly suspicious circumstance of the young man's hurried departure, his refusal to have his boots cleaned, the incident of the L1 note, and the unshakable fact that the footprints leading to and from the pit where the body was discovered had been made by his boots.
"As a further contributory link in the chain of evidence against Ronald, you intend to use the fact that he was turned out of the Grand Hotel, Durrington, the previous day because he couldn't pay his hotel bill, because this fact, combined with the fact that Mr.Glenthorpe showed him the money he had drawn from the bank at Heathfield, supplies a strong motive for the crime.

In this connection you intend to try to establish that the Treasury note which Ronald left to pay his inn bill was one of those in Mr.Glenthorpe's possession, because it happens to be one of the First Treasury issue, printed in black and white, and all Mr.
Glenthorpe's notes were of that issue, according to the murdered man's own statement.

That, I take it, is the police theory of this case." "It is," said Superintendent Galloway.

"You've put it a bit more fancifully than I should, but it comes to the same thing.

But what do you make out of the incident at the Grand Hotel, Durrington, yesterday morning?
You were there, and saw it all.