I miss
that?"

He sprang to his feet and hurried out of the lounge.

CHAPTER 13. A PROMISING CLUE

The consideration which had thus suddenly occurred to Inspector Willis
was the extraordinary importance of the fact that the tall traveller
had spoken through the tube to the driver. He marveled how he could have
overlooked its significance. To speak through a taxi tube one must hold
up the mouthpiece, and that mouthpiece is usually made of vulcanite or
some similar substance. What better surface, Willis thought delightedly
but anxiously, could be found for recording finger-prints? If only the
tall man had made the blunder of omitting to wear gloves, he would have
left evidence which might hang him! And he, Willis, like the cursed
imbecile that he was, had missed the point! Goodness only knew if he was
not already too late. If so, he thought grimly, it was all u.p. with his
career at the Yard.

He ran to the telephone. A call to the Yard advised him that the taxi
driver, on being informed he was no longer required, had left with his
vehicle. He rapidly rang up the man's employers, asking them to stop the
cab directly they came in touch with it, then hurrying out of the hotel,
he hailed a taxi and drove to the rank on which the man was stationed.

His luck was in. There were seven vehicles on the stand, and his man,
having but recently arrived, had only worked up to the middle of the
queue. The sweat was standing in large drops on Inspector Willis's brow
as he eagerly asked had the tube been touched since leaving
Scotland Yard, and his relief when he found he was still in time was
overwhelming. Rather unsteadily he entered the vehicle and ordered the
driver to return to the Yard.

On arrival he was not long in making his test. Sending for his
finger-print apparatus, he carefully powdered the vulcanite mouthpiece,
and he could scarcely suppress a cry of satisfaction when he saw shaping
themselves before his eyes three of the clearest prints he had ever had
the good fortune to come across. On one side of the mouthpiece was the
mark of a right thumb, and on the other those of a first and second
finger.

"Lord!" he muttered to himself, "that was a near thing. If I had missed
it, I could have left the Yard for good and all. It's the first thing
the Chief would have asked about."

His delight was unbounded. Here was as perfect and definite evidence as
he could have wished for. If he could find the man whose finge