"We're not going to break it, Daddy," she answered seriously. They both chorused, "No more leaving this time." But they both broke into giggles! I'll have to watch them. What good it would do, I don't know. They're up to something, yet how can I stop them? Shut them in their rooms? Tan their hides? I wonder what someone else would recommend. * * * * * _Sunday night_ The kids are gone! I've been waiting an hour for them. I know they wouldn't stay away so long if they could get back. There must be something they've run into. Bright as they are, they're still only children. I have some clues. They promised me they wouldn't go out of this present time. With all her mischievousness, Star has never broken a promise to me--as her typically feminine mind interprets it, that is. So I know they are in our own time. On several occasions Star has brought it up, wondering where the Old Ones, the Bright Ones, have gone--how they got off the Moebius Strip. That's the clue. How can I get off the Moebius Strip and remain in the present? A cube won't do it. There we have a mere journey along the single surface. We have a line, we have a plane, we have a cube. And then we have a supercube--a tesseract. That is the logical progression of mathematics. The Bright Ones must have pursued that line of reasoning. Now I've got to do the same, but without the advantage of being a Bright. Still, it's not the same as expecting a normally intelligent person to produce a work of genius. (Genius by our standards, of course, which I suppose Robert and Star would classify as Tween.) Anyone with a pretty fair I.Q. and proper education and training can follow a genius's logic, provided the steps are there and especially if it has a practical application. What he can't do is initiate and complete that structure of logic. I don't have to, either--that was done for me by a pair of Brights and I "simply" have to apply their findings. Now let's see if I can. By reducing the present-past-future of man to a Moebius Strip, we have sheared away a dimension. It is a two-dimensional strip, because it has no depth. (Naturally, it would be impossible for a Moebius Strip to have depth; it has only one surface.) Reducing it to two dimensions makes it possible to travel anywhere you want to go on it via the third dimension. And you're in the third dimension when you enfold yourself in the twisted cube.