Following his glance, Burton saw a slim youthful figure, clad in a light tweed suit and a soft hat, leaning over the rail.
"Well?" he asked.
The constable murmured a name honoured at Scotland Yard.
"Put the case to him, sir," he added; "he can see through most brick walls." Burton hastened to the side of the detective.
"A man on that boat has stolen the secret of the new explosive for the British Navy," he said without preamble. "Can you stop him?"
The detective turned his keen eyes on his questioner and looked hard at him for a moment or two.
"Tell me all about it, sir," he said.
Burton hurriedly related all that had happened. "A cable to Ostend would be enough, wouldn't it?" he asked in conclusion.
"I'm afraid it would hardly do, sir," replied the detective. "Your description is too vague. Tall man about forty, bald, with a hand-bag--there may be dozens on the boat. It would be too risky. We have to be careful. I saw a notorious diamond thief go on board, but I couldn't arrest him, not having a warrant, and nothing certain to go upon. You had better go to the police station, tell the superintendent all you know, and leave him to communicate with the Belgian police in due course."
"And give the thief time to get rid of the stuff! If it once passes from his hands the secret will be lost to us, and any foreign Power may be able to fill its shells with Dr. Micklewright's explosive. It's too bad!"