I went to my quarters and told Zanda to lock herself in after I had left and to open the door only in answer to a certain signal which I imparted to her. She was only too glad to obey my injunction.

When I was ready to leave the building, Hamas conducted me to the outer doorway.

Here he showed me a hidden button set in the masonry and explained to me how I might use it to announce my return.

I had gone but a short distance from the house of Fal Sivas when I met Rapas the Ulsio. He seemed to have forgotten his anger toward me, or else he was dissimulating, for he greeted me cordially.

"Where to?" he asked.

"Off for the evening," I replied.

"Where are you going, and what are you going to do?"

"I am going to the public house to get my things together and store them, and then I shall look around for a little entertainment."

"Suppose we get together later in the evening," he suggested.

"All right," I replied; "when and where?"

"I will be through with my business about half after the eighth zode. Suppose we meet at the eating-place I took you to yesterday."

"All right," I said, "but do not wait long for me. I may get tired of looking for pleasure and return to my quarters long before that."

After leaving Rapas, I went to the public house where I had left my things; and gathering them up I took them to the hangar on the roof and stored them in my flier. This done, I returned to the street and made my way toward the address that Fal Sivas had given me.

The way led me through a brilliantly lighted shopping district and into a gloomy section of the old town. It was a residential district, but of the meaner sort.

Some of the houses still rested upon the ground, but most of them were elevated on their steel shafts twenty or thirty feet above the pavement.

I heard laughter and song and occasional brawling-the sounds of the night life of a great Martian city, and then I passed on into another and seemingly deserted quarter.

I was approaching the headquarters of the assassins. I kept in the shadows of the buildings, and I avoided the few people that were upon the avenue by slipping into doorways and alleys. I did not wish anyone to see me here who might be able afterward to recognize or identify me. I was playing a game with Death, and I must give him no advantage.

When finally I reached the building for which I was seeking, I found a doorway on the opposite side of the avenue from which I could observe my goal without being seen.

The farther moon cast a faint light upon the face of the building but revealed to me nothing of importance.

At first, I could discern no lights in the building; but after closer observation I saw a dim reflection behind the windows of the upper floor. There, doubtless, was the meeting-place of the assassins; but how was I to reach it?

That the doors to the building would be securely locked and every approach to the meeting-place well guarded, seemed a foregone conclusion.

There were balconies before the windows at several levels, and I noticed particularly that there were three of these in front of windows on the upper story. These balconies offered me a means of ingress to the upper floor if I could but reach them.

The great strength and agility which the lesser gravitation of Mars imparts to my earthly muscles might have sufficed to permit me to climb the exterior of the building, except for the fact that this particular building seemed to offer no foothold up to the fifth story, above which its carved ornamentation commenced.

Mentally debating every possibility, by a process of elimination, I was forced to the conclusion that my best approach would be by way of the roof.

However, I determined to investigate the possibilities of the main entrance on the ground floor; and was about to cross the avenue for that purpose when I saw two men approaching. Stepping back into the shadows of my hiding-place, I waited for them to pass; but instead of doing so they stopped before the entrance to the building I was watching. They were there but a moment when I saw the door open and the men admitted. This incident convinced me that someone was on guard at the main entrance to the building, and that it would be futile for me to attempt to enter there.

There now remained to me only the roof as a means of entrance to the building, and I quickly decided upon a plan to accomplish my design.

Leaving my hiding-place, I quickly retraced my steps to the public house in which I had been lodging, and went immediately to the hangar on the roof.

The place was deserted, and I was soon at the controls of my flier. I had now to run the chance of being stopped by a patrol boat, but this was a more or less remote contingency; as, except in cases of public emergency, little attention is paid to private fliers within the walls of the city.

However, to be on the safe side, I flew low, following dark avenues below the level of the roof tops; and in a short time I reached the vicinity of the building that was my goal.

Here I rose above the level of the roofs and, having located the building, settled gently to its roof.

The building had not been intended for this purpose, and there was neither hangar nor mooring rings; but there are seldom high winds on Mars, and this was a particularly quiet and windless night.

Leaving the deck of the flier, I searched the roof for some means of ingress to the building. I found a single small scuttle, but it was strongly secured from within, and I could not budge it-at least without making far too much noise.

Going to the edge of the building, overlooking the avenue, I looked down upon one of the balconies directly below me. I could have lowered myself from the eaves and, hanging by my hands, dropped directly onto it; but here again I faced the danger of attracting attention by the noise that I must make in alighting.

I examined the face of the building just below me and discovered that, in common with most Martian buildings, the carved ornamentation offered handholds and footholds sufficient to my need.

Slipping quietly over the eaves, I felt around with my toes until I found a projection that would support me. Then, releasing one hand, I felt for a new hold; and so, very slowly and carefully, I descended to the balcony.

I had selected the place of my descent so that I was opposite an unlighted window. For a moment I stood there listening. Somewhere within the interior of the building I heard subdued voices. Then I threw a leg over the sill and entered the darkness of the apartment beyond.

Slowly I groped my way to a wall and then followed along it until I came to a door at the end of the room opposite the window. Stealthily I felt for the latch and lifted it. I pulled gently; the door was not locked; it swung in toward me without noise.

Beyond the door was a corridor. It was very faintly illuminated, as though by reflected light from an open doorway or from another corridor. Now the sound of voices was more distinct. Silently I crept in the direction from which they came.

Presently I came to another corridor running at right angles to the one I was following. The light was stronger here, and I saw that it came from an open doorway farther along the corridor which I was about to enter. I was sure, however, that the voices did not come from this room that I could see, as they would have been far more clear and distinct had they.

My position was a precarious one. I knew nothing at all about the interior arrangements of the building. I did not know along which corridor its inmates came and went. If I were to approach the open doorway, I might place myself in a position where discovery would be certain.

I knew that I was dealing with killers, expert swordsmen all; and I did not try to deceive myself into believing that I would be any match for a dozen or more of them.