about it for years. We would be shunted away, or even disposed of, in case we talked, and that's not something I fancy at the moment!"

The other men gave their assent. They didn't want to risk losing their skins either.

"Right, then," said Phillip, "We'll head back to base now, and watch the hole opening from there. At the rate it's moving it will be hours before anyone can get down it!"

reluctantly the men resumed their seats and started to turn the huge diggers back towards base.

The big machines trembled as their generators came to life, and the big tracks screwed in the lunar soil as they turned. Soon they were lumbering back in silent echelon, with Phillip in the lead. Each man was silent, locked into his own thoughts, wondering about whether they were really doing the right thing in not reporting this to the authorities. Phillip felt the burden of responsibility the most. What if the false moon unleashed a weapon of destruction on Earth? What if he became responsible for some terrible repercussions connected with the door? What if...?

Whatever the case was, he realized it was too late now to go back.

NINE

Many hours later the door had fallen inwards leaving a long, straight, square hole. Phillip studied it carefully on screen from base and decided it was time to return and investigate on site again. His stomach was churning a little as he organized his team. Ralph said he preferred to stay back, but he tried to make it sound like a joke. Everyone knew he was scared. They were too.

Various things were gathered from the stores, in readiness. Ropes, electric cables, torches, extra oxygen tanks, direction-finders, and simple field-scanners. Phillip was taking everything he considered suitable for a basic caving expedition, but with the added complication that this was no ordinary cave.

All was prepared and they moved out.

Four vehicles pulled to a stop on the surface of the flat. The harsh black and white effect made the hole stand out on perfect clarity. The soundlessness of all operations made the event even more eerie, and the sound of breathing, which filled the men's helmets was almost comforting, as they walked carefully towards the hole.

Phillip went first, laying out a cable and a rope. He reached the edge of the black pit and threw the rope