For a million years the bubble had been growing, like a vast abscess, below the root of the mountains. Now the abscess was about to burst. Captain Harris had left the controls on autopilot and was talking to the front row of passengers as the first tremor shook the boat. For a fraction of a second he wondered if a fan blade had hit some submerged obstacle; then, quite literally, the bottom fell out of his world.It fell slowly, as all things must upon the Moon. The sea was alive and moving . . . Every stage of that nightmare transformation was pitilessly illuminated by the earth light, until the crater was so deep that its firewall was completely lost in shadow, and it seemed as if Selene were racing into a curving crescent of utter blackness – an arc of annihilation.In darkness and in silence, they were sinking into the Moon. . . .