CHAPTER XVII.

PROWLING SHADOWS.

Tad and Nereid had found the apparatus easy to adjust. They tested it before they left Tad’s room; it seemed to work perfectly. It consisted of a long robe of fabric, light as gossamer, dull, dead black. There were four of these robes. Nereid took the smallest. It enveloped her from head to foot; it swept the ground; its sleeves ended in black gloves; its hood covered her head. There was a mask-like flap for her face; small, transparent black panes for eyes; a clip against her nostrils to hold a breathing valve in place.

“All right, Nereid?”

“Yes.”

Around her waist Tad adjusted a narrow black belt. It was a rope of interlaced, tiny black wires. A black curved box like a battery was fastened to the belt. Light in weight--all dead black. There were a dozen dangling black wires. Tad connected them at her shoulders, along her arms to the waist, down to the hem of the robe, and up to the crest of the hood. She stood, in the dim light of Tad’s room, a black grotesque blob of shape against the wall. Fantastic, hooded little figure merging with the shadows. But she was plainly to be seen--the outlines of her, blotting out the table and the wall behind her. An inky silhouette.

[Illustration: _The fantastic hooded figure began merging with the shadows._]

She said: “I’ll turn it on.” Her gloved hand fumbled with the battery. The current went into the robe. It glowed luminous for a moment. The shape of her was there, shimmering like a silver ghost. Misty--a fog dissolving--gone! The table and the wall behind her showed clearly; there was nothing to be seen in front of them.

It was uncanny. Tad said sharply: “Nereid, you all right?”

“Yes, Tad.”

Her voice, calm, from the empty air. Tad reached out his hand and, fumbling, came upon her. The robe was vaguely vibrating.

“It works, Nereid! I can’t see you! Stand back, close against the wall.”

He could faintly make out the distorted blur of her shape as she backed nearer the table and wall; the table outlines were distorted; the wall seemed to have a shadow on it.

“That’s too close, Nereid. We must remember that--keep away from things.”

There is one of these robes now in the Anglo-American Museum of Science, in London. Apparently it cannot be duplicated. But the fundamental principle of its operation is simple. The electrification of the fabric--vibrations of an unknown current akin to what we call electricity--set up in the air surrounding the robe, a magnetic field. As Nereid stood in the center of Tad’s room, the light rays from the table and wall behind her were bent around this magnetic field so that their image was carried unbroken to Tad’s sight. It was only when she stood too close to the wall that its light rays were blocked by the solidity of her.

The robe itself reflected no light rays. The color we call black is no color at all, but merely the absence of all colors--black, because it absorbs almost all the color-bearing light rays which strike it. There is, however, generally a glint, high lights and shadows. But this robe, with the current into it, reflected no light rays, no tiny glint from its folds.

And with these two principles, for practical purposes it was invisible. Nothing really eerie or uncanny. Solid science, strange but rational. The bending of light rays for a century has been observed and understood by our astronomers. Our sun itself has a similar magnetic field about it, bending the light rays from the distant stars which in reality are behind the sun, but seem to be off to one side.

Tad was triumphant. Nereid helped him adjust his robe. He carried under it two others--for Arturo and me--carefully folded and tied around his body.

Nereid was a little doubtful and cautious. “We must remember what they told my father--in the real darkness we Middge, and the Gians, are keener of vision for very close objects.”

They were both standing with the current turned on. Nereid put out a tentative hand. “Even in this light I can--I almost think I see you, Tad.”

* * * * *

They started from the house, invisible shadows, walking quietly, hand in hand not to lose each other. The streets were in a confusion of excitement. Middge couriers had aroused the people to the necessity of leaving. The houses showed bustling, frantic activity. Middge families, with household treasures piled on their _arras_, were starting for the open country. The beginning of the flight. Men, women and children, with impedimenta that very soon would be discarded, plodding away. A long line of them, assembled in an open, parklike space, started marching off. There was another street, up which a line of Gians was headed for the fortress garden. The Middge avoided them. The Gians, intent upon their own activities, took no notice of any one.

Through it all Tad and Nereid moved unseen. There was no danger, save for a chance collision. They came to the garden. The lower windows of the Castle were barred; the upper ones were open. The garden was bustling with activity. A huge aërocar was being loaded.

Tad whispered: “The main door is open. That’s the best way in.”

Gians were passing in and out. Tad and Nereid cautiously mounted the steps. They kept near the edge. At the top a man suddenly came out; he nearly ran into them. Tad pulled Nereid hastily aside; they stood at the doorway, pressed against the wall. Tad clung to her; he could not see his outstretched arm; nor her. He whispered:

“Careful, Nereid; he nearly hit us.”

In the doorway a group of Gian women were talking. One of them looked squarely at Tad. His heart leaped; but she idly looked away.

Nereid whispered: “Wait just a moment--I can hear them--”

They were talking of the Middge attack upon the gate-house. Gians had been sent to repulse it. That accursed Bhool!

One of the women spoke softly to her companions; abruptly they were all looking toward Tad and Nereid. Too close to the wall! He realized it. The women saw something--puzzling shadows.

“Nereid! Move!”

They moved soundlessly into the doorway. The women went on talking. Clinging together, the two slipped past.

They were in the Castle. A dim entryway. It was thronged with people. Nereid was frightened. It was difficult to avoid being run into--and to avoid getting too near anything.

“This way,” Tad whispered. He drew her toward a side corridor. In a few minutes they would reach our cell.

Abruptly Nereid stopped.

“What is it?” he whispered.

“Wait! Listen--”

He heard nothing but the babble of Gian voices. But Nereid’s hearing was keener.

“Jeff,” she whispered. “I hear his voice.”

* * * * *

She led Tad across the room; they threaded their way, infinitely dangerous. They came to a broad doorway, its door ajar. They did not dare open it. They waited, crouching aside from the passing people. The door opened presently; a woman looked in for a moment.

“Nereid--now!”

They slid through the doorway. Tad saw me sitting beside Rhana, with three men guards standing over me!

There was no one else in the room. Tad and Nereid found a place to crouch. They listened to our talk, waited, hoping to find a way to get at me and help me escape. A sudden rush at these guards--

Tad had brought Nereid because if blank darkness were encountered in the Castle corridors underground, Nereid would be able to guide him. He was sorry now that he had brought her. Had he been alone--a leap on these guards; he and I fighting our way out--

But Arturo? Where was Arturo, since I was not in the cell, but up here?

Nereid, crouching silently, reached me with her thoughts, but she must have reached Rhana also. Nereid, intently thinking, had crept forward close to the table; Tad still clung to her. Rhana suddenly put out the lights. Tad was confused. He decided to make a sudden rush for me. He even brushed me with his robe, but Nereid pulled him away. Her mind, her whole heart now, instinctively was for Arturo.

And Tad agreed it was better. My thoughts had given Nereid the information she sought.

She and Tad moved swiftly for the door. It was partly open now; they slid through. They would get Arturo and come back for me.

In the dark corridors they moved more freely. They crossed the bridge, went down the incline, came to Arturo’s cell. The route was what my thoughts of it had given them, for this was not the cell Bhool had described. Even in that he had lied to Tad.

The cell door could be opened from the corridor side. They found Arturo, and robed him like themselves.

They were ready. Nereid stood listening. From overhead came muffled sounds, cries, running feet.

They left the cell and crept back along the corridor. Tad was leading. At a sharp corner he ran full into me!