-the fluttering
cards, the quick, unconscious gesture of concealment, and the startled
glance which so plainly reflected the dread of discovery. No! there was
no mistake there, but the explanation lay deeper.

They had reached the angle of the narrow passage which led to the front
outlet of the offices. A small window was fixed at the dark turn of the
long dark corridor to admit light. Colwyn chanced to glance through this
window as he reached it, and his quick eye took in the figure of a man
standing motionless in a narrow alley of the side street below. He was
almost concealed behind an archway, but it was apparent to the detective
that he was watching the corner building. As Colywn looked at him he
slightly changed his position and his face came into view. With a quick
imperative gesture to his companion, Colwyn ran swiftly along the
remainder of the corridor and down the flight of stairs into Hatton
Garden.

Caldew followed more slowly, puzzled by the other's strange action. When
he reached the doorway Colwyn was nowhere to be seen, so he waited in
the entrance. After the lapse of a few minutes he saw Colwyn returning
from the direction of Clerkenwell.

"He has got away," he said, as he reached Caldew. His voice was a little
breathless, as though with running.

"He? Who?"

Colwyn drew him into the empty entrance hall before he answered:

"Nepcote. He was watching outside. I saw him through the upstairs
window. He either followed us here or has been waiting to see if we
came. I should have foreseen this."

A flicker of unusual agitation on Colwyn's calm face increased Caldew's
mental confusion.

"I don't understand," he stammered. "He--Nepcote--why should he be
watching us?"

"Because he penetrated the truth last night. He knew he was in danger."

"But why should he follow us here?"

"He accidentally dropped some cards from his pocket-book when giving
Merrington an address at his flat last night, and one of them was
Wendover's business card. Merrington did not see it--it would have
conveyed nothing to him if he had--but I did. Nepcote knew that I saw
it, and must have realized that I suspected him. He has been watching my
rooms and followed us here, or he has been hanging around this place to
see if I called on Wendover."

"Even now I do not see the connection. If Wendover told us the truth,
Nepcote has not been to him with the necklace. Then what did it matter
to Nepcote whether you came here or not?