The two other children--Martynn and Francine--were twins, now just seventeen. Alike, physically and temperamentally, as children of a birth traditionally should be. Slim and rather small--Martynn about my height; Francine somewhat shorter. Both blue-eyed, with blond hair. Francine's hair was long-waving tresses which she wore generally in plaits over her shoulders; Martynn's was short and curly. They were rather alike of feature; a delicacy of mold which gave to Martynn a girlishness. But not an effeminacy, for he was a young daredevil; and his sister hardly a lesser one. In childhood and adolescence an impish spirit of deviltry had always seemed to possess these twins; a spirit of mischief which had made them a great trial to their father. It had turned, now that they were nearing maturity, into an apparent desire for reckless adventure--the product of abounding health, and bubbling, irrepressible good nature. They adored each other; were constantly together, with youthful escapades threatening limb and life and complete disaster, out of which they would emerge or be extricated with dauntless spirits unperturbed. The greater maturity of womanhood at seventeen had brought to Frannie moments of gentleness, sweetness and a simple dignity. But they were brief moments, and no more than a word or look from her twin was needed to dispel them. Martt himself was without a vestige of dignity. But they were no fools, these twins. They could, upon strict necessity, give sober, intelligent thought to any problem at hand (Martynn had won honors at the Great-London University); but of sober, matured action they were incapable. Fearless--unreasonably fearless. But irresistible, likable, and apparently quite capable of being restrained. A word from Dr. Gryce, or from Brett--and to a lesser extent from me who had known them from childhood--brought instant though often very temporary obedience. They considered themselves quite grown up now. In truth, at seventeen, Frannie was to my eyes a really beautiful young woman. II We sat in a little arbor beside the house, with its breakfast table already laid. Dr. Gryce, Brett, and myself. Martt was with Frannie preparing the meal. It was evidence of the simplicity which marked the Gryce household. In these days of mechanical devices for almost everything--and the usual multiplicity of servants--there was not a meal prepared for Dr. Gryce save by his daughter. I was very curious to learn why they had sent for me; but I had no need to question, for at once Dr. Gryce plunged into it. "I hope, Frank, that you can stay--well, at least a few days with us. Can you?" I stared. The Day Officer of the Manhattan Interplanetary Postal Division was undoubtedly already in a rage at my absence. I said so. "A few days? Dr. Gryce, I dread every conjunction that brings these accursed mails--my divisional officers think it's a crime even to eat or sleep when a planet is near us."