Peter gulped and stared, knowing that Mr. Caxton did not really expect an answer. "Peter," Mr. Caxton went on. "The first space rocket reached Mars in nineteen ninety-seven. This is the year twenty fifty-three. Fifty years is a long time, Peter. In all those years no man or _boy_ has ever seen a Martian animal. "Do you know why, Peter?" Mr. Caxton gave Peter's arm a slight wrench. "I'll tell you why. A man requires so much gaseous oxygen to support his life that he can't walk twenty yards on Mars without an oxygen mask. He'd drop dead if he tried to walk a mile. You can build fires if you bank them carefully, but a man needs more oxygen than a fire." Mr. Caxton's eyes narrowed in malicious triumph. "No animal the size of man or larger could exist on Mars without some kind of natural oxygenating apparatus built into its body. "A bird? Peter, I'm going to be completely honest with you. A certain kind of bird might just possibly be able to survive on Mars, but it would have to get along on very little oxygen." With an effort Peter summoned the courage to interrupt Mr. Caxton with a quite unnecessary reminder. "It _was_ a bird, Mr. Caxton. I told you it had feathers!" "Yes indeed, Peter. It was a bird you saw. You say you saw a _huge_ bird standing in the doorway. Do you realize what a perfect pit you have just dug for yourself? Do you know what a Martian bird would look like? Have you ever tried to imagine how a _real_ scientist feels when he knows that he can't be wrong? Here, I'll show you!" With his gaze fixed triumphantly on Tommy Mr. Caxton removed a small writing pad from his weather jacket, and proceeded to draw upon it. Mr. Caxton used an ordinary lead pencil, and that his skill as an artist was of no mean order could be seen almost instantly. With a few deft strokes Mr. Caxton traced out on the smooth paper a shape of incredible lightness and grace, a shape so fragile, slender and spiraling that only a miracle of the glass-blower's art could have translated it into three-dimensional reality. A veritable wonder bird it seemed, a creature of light and fire with a bill three times the length of its body. With skill in the arts there goes usually a certain gentleness, a generosity of spirit which shrinks from inflicting pain on others. But so closely was Mr. Caxton's skill linked to the cruelty in his nature that he always saw to it that it aroused in the beholder bitterness and despair. Mr. Caxton did not ask Peter how he liked the drawing. Instead, he thrust it at him, twisting him about and forcing him to stare at it. "A Martian bird would look like that," he said, with cold mockery in his stare. "Did the bird you claim to have seen look like that? Did it? Answer me!" "No!" Susan cried. "You keep out of it!" Mr. Caxton warned. "I'm waiting, Peter." "No, it didn't," Peter said. "Pop wouldn't want me to say it did. He told me an explorer has to observe closely everything he sees."