For the better part of their journey to town Caldegard and Randal Bellamy ate their hearts in silence. The road was good, and they had it almost to themselves.

As they were nearing London, Caldegard spoke.

"Bellamy," he said, "that brother of yours won't stop at killing if——"

"He'll begin with it," replied Randal, "if he gets a fair chance."

"It gives me unreasonable hope," said Caldegard.

"Men who've trusted Dick would call your hope reasonable."

"Yet he's sent us after Ambrotox," complained the father, "and my heart's breaking for my little girl."

"His argument convinced you, anyhow," said Randal.

At New Scotland Yard Sir Randal's card gained them instant admission to the presence of the Superintendent of the Criminal Investigation Department.

He listened without a word to Randal's compact and lucid statement of the facts.

"It's a good thing I was kept here so late to-night, gentlemen," he said. "We shall act without losing a moment in the matter of your daughter's disappearance, Dr. Caldegard. But the theft of your secret, of which both Sir Charles Colombe and the Home Secretary have spoken to me, is a matter of such tremendous importance, that I am obliged to communicate immediately with both these gentlemen and the Commissioner. And you will be doing me a great kindness if you will both remain here until I hear from them."

An hour later a sombre group of six, after protracted discussion, seemed almost to have exhausted the evidence, suggestion and counsel which could be brought to bear upon a crime so sudden and so obscure.

Sir Charles Colombe looked anxiously round him as he spoke.

"That is the danger," he said, "which we have to face: that these foul pests of society should escape with Professor Caldegard's discovery and master his secret—a peril to which all the dangers mankind has run since the world began from greed, bigotry, alcohol and opium are child's play. The bill of which Sir Gregory has just spoken would give us powers to lay hands on all these local branches of what Superintendent Finucane has described as 'the Dope Gang.' We know already some twenty-five or thirty of them. If we were as well advanced in our knowledge of their central organisation, we might even now do something fairly vigorous under the law of conspiracy. As it is, we can only proceed against individuals trafficking in and supplying certain specified drugs. The secret of this greatest drug of all must not, if human power can prevent it, come into the hands of the inner ring before we have our grip on it. Needles, before now, have been successfully hunted in haystacks, and perhaps even you, Professor Caldegard, have no adequate conception of how close the meshes are in the net Superintendent Finucane is spreading. And I should like you to understand, sir," he said, drawing nearer to the old man who sat staring with fixed eyes out of a ghastly face, "that, though our duty makes us think of millions where you can think only of one, every effort which the Criminal Investigation Department makes, every trap it lays, every device it contrives to recover your property is equally adapted to finding your daughter. In your fear for her safety you have forgotten your drug; in our fear for the drug we cannot let your daughter out of our minds."

"She may be—dead," said Caldegard.

The Superintendent answered him.

"I don't believe it," he declared. "You see, sir, the thief's plan worked smoothly, bar the one unexpected factor—the young lady in the room. If he didn't kill her then, he don't mean to kill her."

"That's my brother's argument," said Randal, adding his word of comfort.

There was a tap at the door, and a constable entered.

"Sir Randal Bellamy's chauffeur, sir," he said to Finucane. "He has brought this letter. Says it's from Mr. Richard Bellamy."

Randal glanced at the note and then read aloud:

"From my brother Richard," he said. "Dr. Caldegard knows this Melchard, I believe."

When Caldegard had told them all he knew of the man, the Superintendent looked at the Commissioner,

"I think, sir," he said, "we'd better inquire about Mr. Alban Melchard."

"Rather a wildgoose chase," grumbled the Home Secretary.

"I shouldn't wonder, sir," replied Finucane, "if Mr. Richard Bellamy isn't a very wideawake young gentleman."