“I suppose,” said the cunning young man, “that it isn’t possible to ask me to be a fourth?”

“You will be a fifth,” she smiled. “Mr. Johnson is coming down too. Poor Mr. Johnson is scared of father, and I think the fear is mutual. Father resembles Maitland in that respect, that he does not like strangers. I’ll invite you anyway,” she said, and the prospect of the Sunday meeting cheered her.

Elk came to see him that night, just as he was going out to a theatre, and Dick related the girl’s suspicion. To his surprise, Elk took the startling theory very coolly.

“It’s possible,” he said, “but it’s more likely that the tattoo mark isn’t a frog at all. Old Maitland was a seaman as a boy—at least, that is what the only biography of him in existence says. It’s a half-column that appeared in a London newspaper about twelve years ago, when he bought up Lord Meister’s place on the Embankment and began to enlarge his offices. I’ll tell you this, Mr. Gordon, that I’m quite prepared to believe anything of old Maitland.”

“Why?” asked Dick in astonishment. He knew nothing of the discoveries which the detective had made.

“Because I just should,” said Elk. “Men who make millions are not ordinary. If they were ordinary they wouldn’t be millionaires. I’ll inquire about that tattoo mark.”

Dick’s attention was diverted from the Frogs that week by an unusual circumstance. On the Tuesday he was sent for by the Foreign Minister’s secretary, and, to his surprise, he was received personally by the august head of that department. The reason for this signal honour was disclosed.

“Captain Gordon,” said the Minister, “I am expecting from France the draft commercial treaty that is to be signed as between ourselves and the French and Italian Governments. It is very important that this document should be well guarded because—and I tell you this in confidence—it deals with a revision of tariff rates. I won’t compromise you by telling you in what manner the revisions are applied, but it is essential that the King’s Messenger who is bringing the treaty should be well guarded, and I wish to supplement the ordinary police protection by sending you to Dover to meet him. It is a little outside your duties, but your Intelligence work during the war must be my excuse for saddling you with this responsibility. Three members of the French and Italian secret police will accompany him to Dover, when you and your men will take on the guard duty, and remain until you personally see the document deposited in my own safe.”

Like many other important duties, this proved to be wholly unexciting. The Messenger was picked up on the quay at Dover, shepherded into a Pullman coupé which had been reserved for him, and the passage-way outside the coupé was patrolled by two men from Scotland Yard. At Victoria a car, driven by a chauffeur-policeman and guarded by armed men, picked up the Messenger and Dick, and drove them to Calden Gardens. In his library the Foreign Secretary examined the seals carefully, and then, in the presence of Dick and the Detective-Inspector who had commanded the escort, placed the envelope in the safe.

“I don’t suppose for one moment,” said the Foreign Minister with a smile, after all the visitors but Dick had departed, “that our friends the Frogs are greatly interested. Yet, curiously enough, I had them in my mind, and this was responsible for the extraordinary precautions we have taken. There is, I suppose, no further clue in the Genter murder?”