"But I understood that it had been opened with a key?"

"That's so. They tried to force it, but couldn't. And, in the end, they must have got it unlocked somehow or other."

"Curious," said Poirot, his eyes beginning to flicker with the green light I knew so well. "Very curious! They waste much, much time trying to prise it open, and then - sapristi! they find that they have the key all the time - for each of Hubbs's locks are unique."

"That's just why they couldn't have had the key. It never left me day or night."

"You are sure of that?"

"I can swear to it, and besides, if they had had the key or a duplicate, why should they waste time trying to force an obviously unforceable lock!"

"Ah! there is exactly the question we are asking ourselves! I venture to prophesy that the solution, if we ever find it, will hinge on that curious fact. I beg of you not to assault me if I ask you one more question: Are you perfectly certain you did not leave the trunk unlocked?" Philip Ridgeway merely looked at him, and Poirot gesticulated apologetically.

"Ah, but these things can happen, I assure you! Very well, the bonds were stolen from the trunk. What did the thief do with them? How did he manage to get ashore with them?"

"Ah!" cried Ridgeway. "That's just it. How? Word was passed to the Customs authorities, and every soul that left the ship was gone over with a toothcomb!"

"And the bonds, I gather, made a bulky package?"

"Certainly they did. They could hardly have been hidden on board - and anyway we know they weren't because they were offered for sale within half an hour of the Olympia's arrival, long before I got the cables going and the numbers sent out. One broker swears he bought some of them even before the Olympia got in. But you can't send bonds by wireless."

"Not by wireless, but did any tug come alongside?"

"Only the official ones, and that was after the alarm was given when every one was on the lookout. I was watching out myself for their being passed over to some one that way. My God, Monsieur Poirot, this thing will drive me mad! People are beginning to say I stole them myself."

"But you also were searched on landing, weren't you?" asked Poirot gently.

"Yes."

The young man stared at him in a puzzled manner.

"You do not catch my meaning, I see," said Poirot, smiling enigmatically. "Now I should like to make a few inquiries at the Bank."

Ridgeway produced a card and scribbled a few words on it.

"Send this in and my uncle will see you at once."

Poirot thanked him, bade farewell to Miss Farquhar, and together we started out for Threadneedle Street and the head office of the London and Scottish Bank. On production of Ridgeway's card, we were led through the labyrinth of counters and desks, skirting paying-in clerks and paying-out clerks and up to a small office on the first floor where the joint general managers received us. They were two grave gentlemen, who had grown gray in the service of the Bank. Mr Vavasour had a short white beard, Mr Shaw was clean shaven.