ll Pop lowered the supplies down the long cable
into the Big Crack to the colony far down inside, and freshened up the
landing field marks with magnesium marking-powder if a rocket-blast had
blurred them. That was fundamentally all he had to do. But without him
the mine down in the Crack would have had to shut down.

The Crack, of course, was that gaping rocky fault which stretches nine
hundred miles, jaggedly, over the side of the Moon that Earth never
sees. There is one stretch where it is a yawning gulf a full half-mile
wide and unguessably deep. Where Pop Young's shack stood it was only a
hundred yards, but the colony was a full mile down, in one wall. There
is nothing like it on Earth, of course. When it was first found,
scientists descended into it to examine the exposed rock-strata and
learn the history of the Moon before its craters were made. But they
found more than history. They found the reason for the colony and the
rocket landing field and the shack.

The reason for Pop was something else.

The shack stood a hundred feet from the Big Crack's edge. It looked like
a dust-heap thirty feet high, and it was. The outside was surface
moondust, piled over a tiny dome to be insulation against the cold of
night and shadow and the furnace heat of day. Pop lived in it all alone,
and in his spare time he worked industriously at recovering some missing
portions of his life that Sattell had managed to take away from him.

He thought often of Sattell, down in the colony underground. There were
galleries and tunnels and living-quarters down there. There were
air-tight bulkheads for safety, and a hydroponic garden to keep the air
fresh, and all sorts of things to make life possible for men under if
not on the Moon.

But it wasn't fun, even underground. In the Moon's slight gravity, a man
is really adjusted to existence when he has a well-developed case of
agoraphobia. With such an aid, a man can get into a tiny, coffinlike
cubbyhole, and feel solidity above and below and around him, and happily
tell himself that it feels delicious. Sometimes it does.

But Sattell couldn't comfort himself so easily. He knew about Pop, up on
the surface. He'd shipped out, whimpering, to the Moon to get far away
from Pop, and Pop was just about a mile overhead and there was no way to
get around him. It was difficult to get away from the mine, anyhow. It
doesn't take too long for the low gravity to tear a man's nerves to
shreds. He has to