The discovery of a dwindling alien population living on the lunar surface was a great surprise to the governments of Earth and the CSM. A year has gone by and once again the CSM has been called back to the Moon, but this time they must work with their newly found allies in investigating some of the satellite's mysteries. The discovery of the alien race who call themselves the Harra'shhh'an on the lunar surface was an eye opening experience to humanity. It once and for all settled the human question, are we alone? Not only is humanity not alone, but they are about to discover that there is an intelligence which watches them closely and threatens their very existence.The Moon is not what it appears to be and the CSM must discover its true secret if humanity is to survive and prosper. But what they find threatens to turn all that mankind thought he knew about their satellite upside down. Humanity has already come to grips with the fact that they were not the first dominant species to have evolved on the planet, but this new discovery has even greater consequences. Now the CSM must reach into the Moon's depths and face this enemy on its very own turf. Will the Marines have what it takes to save humanity or are they destined to suffer the same fate as their allies? No one knows the answer, but the CSM will answer the call.