Return trips always seem shorter than departures. There were no more surprises and wonders to slow down time. Even though he felt awe as he watched the reverse sequence of what he had seen before-the disappearance of the dome, the return of the barred windows, the formation of doors and beds, the flickering of days and nights-his thoughts were elsewhere.

His confused thoughts that gradually formed a crucial question.

The end of the voyage came abruptly once again, just as when he arrived in the future. At first, while his eyes were still blinded by the flashes, he could not make out anyone on the other side of the cell. Icy fingers of horror tightened around his chest. What if he wasn't there anymore? If he had only been playing with him? That would be just like the tempter. Then he never would know....

"So?" came a gentle voice from the darkness.

He tried to muffle the sigh of relief, but such effort was futile in the murky silence of the night. "You said the observatory would be named after me, didn't you?" There was no time to beat around the bush; he had to get straight to the point.

"Yes."

"Why?"

"What do you mean?"

"Because of the discovery I made or because I was burned at the stake for not renouncing it?"

"For both one and the other, although considerably more for the act of sacrifice. You know, in the age you just visited, your discovery has only historical value. It has not been refuted, but it is secondary, insignificant, almost forgotten. As you have seen, things have advanced much farther. But your burning will not be forgotten."

From somewhere in the heart of the monastery came the sound of heavy footsteps. It was not just two guards. A larger group was walking through the corridors.

"Does that mean I have no choice?" asked the prisoner quickly. "If the observatory is named after me because I was burned at the stake, then it necessarily follows that there is no way I can avoid that fate. But I can still do it. I still have free will. They're coming. What if I say yes when they ask me to renounce my discovery? That would spare me from the stake but would change the future, wouldn't it? And the future cannot be changed; I saw it with my own eyes."

The steps stopped for a moment, and then in the distance echoed the harsh sound of a barred partition door being opened.

"That's right. You can't change what you saw. And you saw only what is irrefutable, what you cannot influence in any way. What you did not see, however, is whether the observatory is named after you."

The prisoner opened his mouth to say something, but nothing came out. His sight had returned in the meantime, so that now in the obscure light of dawn pouring in from the high window he could make out the contours of his visitor. His head was somehow elongated, as though he had something tall on it.

"No, I did not deceive you, if that's what you're thinking," he continued. "The observatory really will be named after you if you are burned at the stake. But if you are not, it will be named after someone else. One of your students, for example, who will be braver than you. There is no predetermination. Your free will determines what will happen. You will choose between a horrible death in flames and the penitent life of a royal astronomer under the wing of the church, whose comfort will be disturbed only by the scorn of a handful of students and perhaps a guilty conscience: between satisfying your own conceit and the wise insight that it actually makes no difference whom the observatory is named after. I do not envy you. It is not an easy choice."

The rumbling steps stopped in front of the cell door, and a key was thrust into the large lock.

"You know what I will decide?" said the prisoner hurriedly in a soft voice. It was more a statement than a question.

"I know," answered the gentle voice.

The rusty hinges screeched sharply, and into the small cell came first a large turnkey with a torch raised high and after him two Inquisition interrogators in the purple robes of the high priesthood. The soldier who came in last was also holding a torch. There was no more room inside, so the three remaining soldiers had to wait in the corridor.

In the smoky light the prisoner squinted hard at the figure on the bed across from him. The strange object on his head was some sort of cylindrical hat with a wide brim, and its slanted shadow completely hid the man's face.

He had not expected his visitor to stay there. Would he let the others see him? But no one paid any attention to him, as though he were not there, as though he were invisible. In other circumstances this would have confused the prisoner completely, but owing to his recent experience he accepted it as quite natural.

"Lazar," said the first priest, addressing him in an official tone, "this is the last time you will be asked: do you renounce your heresy and penitently accept the teachings of our Holy Mother the Church?"

The prisoner did not take his eyes off the figure in black, but he had turned into a statue. He sat with head bowed, silent, just like an old man who had fallen asleep, with his white hands leaning on the top of his cane. He seemed indifferent, as if all this had nothing to do with him, as though he were not the least bit interested. The silence became heavy from the tenseness, the expectation.

And then, finally, the royal astronomer slowly turned toward the inquisitors and gave his monosyllabic answer.