another taxi."

"I'm afraid you'll find that difficult, sir." The hotel porter shook his
head. "You see how the fog is--we always get them thick about here--it's
rather late in the year for fogs..."

Tarling cut short his lecture on meteorology, buttoned up his coat, and
turned out of the hotel in the direction of the nearest underground
station.

The hotel to which he had taken the girl was situated in a quiet
residential street, and at this hour of the night the street was
deserted, and the fog added something to its normal loneliness.

Tarling was not particularly well acquainted with London, but he had a
rough idea of direction. The fog was thick, but he could see the blurred
nimbus of a street lamp, and was midway between two of these when he
heard a soft step behind him.

It was the faintest shuffle of sound, and he turned quickly.
Instinctively he threw up his hands and stepped aside.

Something whizzed past his head and struck the pavement with a thud.

"Sandbag," he noted mentally, and leapt at his assailant.

As quickly his unknown attacker jumped back. There was a deafening
report. His feet were scorched with burning cordite, and momentarily he
released his grip of his enemy's throat, which he had seized.

He sensed rather than saw the pistol raised again, and made one of those
lightning falls which he had learnt in far-off days from Japanese
instructors of ju-jitsu. Head over heels he went as the pistol exploded
for the second time. It was a clever trick, designed to bring the full
force of his foot against his opponent's knee. But the mysterious
stranger was too quick for him, and when Tailing leapt to his feet he was
alone.

But he had seen the face--big and white and vengeful. It was glimpse and
guess-work, but he was satisfied that he knew his man.

He ran in the direction he thought the would-be assassin must have taken,
but the fog was patchy and he misjudged. He heard the sound of hurrying
footsteps and ran towards them, only to find that it was a policeman
attracted by the sound of shots.

The officer had met nobody.

"He must have gone the other way," said Tarling, and raced off in
pursuit, without, however, coming up with his attacker.

Slowly he retraced his footsteps to where he had left the policeman
searching the pavement for same clue which would identify the assailant
of the night.

The constable was using a small electric lamp which he had taken from his
pocket.

"Nothi