Book 2 in the series is here
Met Driscoll meets with the aliens again. This time the Earth is in peril. He learns that the Moon is an artificial creation of an ancient evil race.
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As Met returned, the outer gear or space suits melted away from the aliens like some magic trick. The creatures were surprisingly human-like in their appearance but with scaled light green skin.
A slowly rotating 3D hologram of the Moon hung in the air in front of the nearest alien. "This Moon of yours exposed your history. It should have been obvious to us from the beginning. The Moon's mass is only 1.2 percent of the Earth while being 25 percent of the diameter. Your Moon is artificial. The mantle is filled with space, like the space in this ship, not empty but hollow."
"Dude! Are you nuts? The Moon is just the Moon. I don't understand. What do you mean exposed us? What does this have to do with me?" Met replied.