"Confusing at first, isn't it? But you'll soon--" "Please!" begged Dirk hoarsely. "I must see--" He placed the mirrorlike object once more to his eyes, saw Graed Garroway lead the way from the execution chamber. Awkwardly, uncertainly, Morris took a step forward ... another. Though he knew his feet trod the soil of the planet Nadron, to his eyes it seemed he glided forward across the floor of the prison. The door swung to behind Garroway and his followers, and involuntarily Dirk flinched ... then grunted reproof at his own needless gesture. So far as he was concerned, that heavy metal barrier did not exist. For the briefest fraction of an instant his vision was blotted by jet darkness, then he stood outside the door, looking down the corridor. He hastened forward, stumbling, as feet that appeared to be traversing smooth floors actually trod uneven soil, and paused at last, an invisible presence at the tableau next enacted. He witnessed his friends' release from the cell, read the movement of Hardesty's dry lips as Neil whispered, "_It ... it is over?_" He saw Garroway's boastful warning, Brian's hot denial, then watched--first with dazed incomprehension, then with fierce understanding--the betrayal, panic and execution of Fred Meacher. * * * * * When Meacher's corpse lay on the floor at ... or so it seemed ... his very feet, and the comrades left the hallway, he would again have followed them. But at that moment he landed with a solid bump against something hard, and with a start he looked from the crystal to find a tree before him. More than a hundred yards away waited those who had befriended him. He retraced his steps slowly to their company. "Now you understand and believe, my boy?" the kindly alien asked. "I believe," said Dirk simply. "But, sir--" "My name, man of Earth, is Slador. On this world, I am known as the Ptan Slador, which is to say 'teacher.' This is my daughter, Rima." "I am called Morris. Dirk Morris. I also--" Dirk spoke bitterly--"have a number, as have all Earthmen of this unhappy century. Yes, Ptan Slador, I believe, but even yet I do not understand. I stand in one world, but looking through your crystal I see into another: my own. Why is this?" "Because, Dirk Morris, our two worlds lie adjacent." "Adjacent? You mean in Space?" "I mean in Space-Time. Look, my young friend ... your Earth science knows of the atom?" "But of course. It is the building-block of matter. The smallest indivisible unit--" "Exactly. Yet even this minute fleck of matter, the building-block of worlds, so small that it cannot be observed under man's strongest microscopes, is composed of ninety-nine per cent _empty space_!