The three marched forward. Ildefonse sent a flux of light into the passage, and started forward, but Rhialto held him back. "One moment!" He indicated a double line of foot-prints in the fine sand which covered the floor of the cavern.

"Sarsem, did you leave these marks?"

"Not I! When I left the cavern, the sand showed a smooth surface."

"Then I deduce that someone has entered the cave after you departed. This person might well have been Hache-Moncour, to judge by the evidence of his boots."

Sarsem drifted into the cavern, making no marks upon the sand. He returned almost at once. "The Perciplex is not where I placed it."

Rhialto and Ildefonse stood stiff with disappointment. "This is dismal news," said Ildefonse. "You have not dealt well with your assigned duty."

"More to the point," said Rhialto, "where now is the Perciplex? In the past, or in the present, or has it been destroyed?"

"Who could be reckless enough to destroy the Blue?" muttered Ildefonse. ' 'Not even an archveult. I believe that the Perciplex is somewhere extant."

"I am inclined to agree," said Rhialto. "Sarsem, in regard to these footprints: from their direction it seems that they were formed before the cavern's mouth was covered—which is to say, the 16th Aeon."

"True. I can also say this: if they were made by someone hoping to find the Perciplex, he failed. The tracks enter the cave, pass the niche where I concealed the prism, continue into the central cavern, wander this way and that in a random pattern, then depart with long strides denoting angry failure. The Perciplex was taken from the cavern prior to the footprints."

Rhialto turned to Ildefonse. "If you recall, Hache-Moncour came to Boumergarth with the subterranean dust still clinging to his boots. Unless he found the Perciplex immediately upon leaving the cave, he failed in his mission."

"Convincing!" said Ildefonse. "Who then took the Perciplex?"

Rhialto said sternly: "Sarsem, your conduct has been less than wise. Need I remind you of this?"

"You need say nothing! In sheer disgust, discharge me from my indenture! The humiliation will be an overwhelming punishment."

"We are not so cruel," said Ildefonse. "We prefer that you make amends by retrieving the Perciplex for us."

Sarsem's lavender face fell. "I must fail you still a second time. I cannot return to the 16th Aeon, because, in effect, I am already there."

"What?" Ildefonse raised high his bristling yellow eyebrows. "I cannot understand."

"No matter," said Sarsem. "The restraints are definite."

"Hmmf," grunted Ildefonse. "We are faced with a problem."

"I observe the single solution," stated Rhialto. "The Preceptor must step back into the 16th Aeon to recover the Perciplex. Ildefonse, prepare yourself! And then—"

"Hold!" cried Ildefonse. "Have you put aside that rationality which once marked your thinking? I cannot possibly leave while turmoil threatens the association! With your keen eyes and rare intelligence, you are the man to recover what is lost! Sarsem, do you not support this point of view?"