Two hours of this exercise left them tired but no richer. "Grandpa," announced Pollux, "this is a lot of left-over country rock."

"Not even that. Most of it's pumice, I'd say."

"Get for home?"

"Check."

They turned the scooter around by flywheel and homed on the City Hall beacon, boosting it up to four hundred miles per hour before. letting it coast, that being the top maneuver they could figure on for the juice they had left in their tanks. They would have preferred to break the speed limit, being uneasily aware that they were late - and being anxious to get home; the best designed suit is not comfortable for too long periods. They knew that their parents would not be especially worried; while they were out of range for their suit radios, they had reported in by the gossip grapevine earlier.

Their father was not worried. But the twins spent the next week under hatches, confined to the ship for failing to get back on time.

For a longer period nothing more notable took place than the incident in which Roger Stone lost his breathing mask while taking a shower and almost drowned (so he claimed) before he could find the water cut-off valve. There are very few tasks easier to do in a gravity field than in free fall, but bathing is one of them.

Dr. Stone continued her practice, now somewhat reduced. Sometimes she was chauffeured by the miner assigned to that duty; sometimes the twins took her around. One morning following her office hours in City Hall she came back into the Stone looking for the twins. "Where are the boys?"

"Haven't seen them since breakfast," answered Hazel. "Why?"

Dr. Stone frowned slightly. "Nothing, really. I'll ask Mr. Fries to call a scooter for me."

"Got to make a call? I'll take you unlessthose lunks have taken our scooter."

"You needn't, Mother Hazel."

"I'd enjoy it. I've been promising Lowell a ride for weeks. Or will it take too long?"

"Shouldn't. It's only eight hundred miles or so out." The doctor was not held down to the local speed limit in her errand of mercy.

"Do it in two hours, with juice to spare." Off they went, with Buster much excited. Hazel allotted one-fourth her fuel as safety margin, allotted the working balance for maximum accelerations, figuring the projected mass-ratios in her head. Quite aside from the doctor's privilege to disregard the law, high speed was not dangerous in the sector they would be in, it being a 'thin' volume of the node.

Their destination was an antiquated winged rocket, the wings of which had been torched off and welded into a tent-­shaped annex to give more living room. Hazel thought that it had a shanty-town air -but so did many of the ships in Rock City. She was pleased enough to go inside and have a sack of tea and let Lowell out of his spacesuit for a time. The patient, Mr. Bakers, was in a traction splint; his wife could not pilot their scooter, which was why Dr. Stone granted the house call. Dr. Stone received a call by radio while they were there; she came back into the general room looking troubled. "'S matter?" inquired Hazel.

"Mrs Silva. I'm not really surprised; it's her first child."

"Did you get the co-ordinates and beacon pattern? I'll run you right-"

"Lowell?"

"Oh. Oh, yes," It would be a long time in a suit for a young­ster.

Mrs Eakers suggested that they leave the child with her.

Before Lowell could cloud up at the suggestion Dr. Stone said, "Thanks, but it isn't necessary. Mr. Silva is on his way here. What I was trying to say, Mother Hazel, is that I probably had better go with him and let you and Lowell go back alone. Do you mind?"

"Of course not. Pipe down, Lowell! I'll have us home in three-quarters of an hour and Lowell can have his nap or his spanking on time, as the case may be."

She gave Dr. Stone one of two spare oxygen bottles before she left; Dr. Stone refused to take both of them. Hazel worked the new mass figures over; with Edith, her suit, and the spare bottle subtracted she had spare fuel. Better hit it up pretty fast and get home before the brat got cranky -

She lined up on City Hall by flywheel and stereo, spun on that axis to get the sun out of her eyes, clutched her gyros, and gave it the gun.

The next thing she knew she was tumbling like a liner in free fall. She remembered from long habit to cut the throttle but only after a period of aimless acceleration, for she had been chucked around in her saddle, thrown against her belts, and could not at first find the throttle.

When they were in free fall again she remembered to laugh. "Some ride, eh, Lowell?"

"Do it again, Grandma!"

"I hope not." Quickly she checked things over. There was not much that could go wrong with the little craft, it being only a rocket motor, an open rack with saddles and safety harness, and a minimum of instruments and controls. It was the gyros, of course; the motor had been sweet and hot. They were hunting the least bit, she found, that being the only evidence that they had just tumbled violently. Delicately she adjusted them by hand, putting her helmet against the case so that she could hear what she was doing.

Only then did she try to find where they were and where they were going. Let's see - the Sun is over there and that's Betelgeuse over yonder - so City Hall must be out that way. She ducked her helmet into the hemispherical 'eye shade' of the stereo. Yup! there she be!

The Eakers place was the obvious close-by point on which to measure her vector. She looked around for it, was startled to discover how far away it was. They must have coasted quite a distance while she was fiddling with the gyros. She measured the vector in amount and direction, then whistled. There were, she thought, few grocery shops out that way - darn few neighbours of any sort. She decided that it might be smart to call Mrs Eakers and tell her what had happened and ask her to call City Hall - just in case.

She could not raise Mrs Eakers. The sloven, she thought bitterly, has probably switched off her alarm so she could sleep. Lazy baggage! Her house looked it - and smelled it, too.

But she kept trying to call Mrs Eakers, or anyone else in range of her suit radio while she again lined up the ship for City, with offset to compensate for the now vector. She was cautious and most alert this time - in consequence she wasted only a few seconds of fuel when the gyros again tumbled.

She unclutched the gyros and put them out of her mind, then took careful measure of the situation. The Eakers dump was now a planetary light in the sky, shrinking almost noticeably, but it was still the proper local reference point. She did not like the vector she got. As always, they seemed to be standing still in the exact center of a starry globe - but her instruments showed them speeding for empty space, headed clear outside the node.

"What's the matter, Grandma Hazel?"

"Nothing, son, nothing. Grandma has to stop and look at some road signs, that's all." She was thinking that she would gladly swap her chance of eternal bliss for an automatic dis­tress signal and a beacon. She reached over, switched off the child's receiver, then repeatedly called for help.

No answer. She switched Lowell's receiver back on. "Why. did you do that, Grandma Hazel?"

"Nothing. Just checking it"

"You can't fool me! You're scared! Why?"

"Not scared, pet Worried a little, maybe. Now shut up; Grandma's got work to do."

Carefully she lined up the craft by flywheel; carefully she checked it when it tried to swing past She aimed both to offset the new and disastrous vector and to create a vector for City Hall. She intentionally left the gyros unclutched. Then she restrapped Lowell in his saddle, checked its position. "Hold still," she warned. "Move your little finger and Grandma will scalp you"

Just as carefully she positioned herself, considering lever arms, masses, and angular moments in her head Without gyros the craft must be balanced just so. "Now," she said to herself, "Hazel, we find out whether you are a pilot - or just a Sunday pilot." She ducked her helmet into the eyeshade, picked a distant blip on which to center her crosshairs, and gunned the craft