The structure found on the Moon was a grim mystery. There was no way of knowing who had built it or what it had been used for. The only certainty was that every man the scientists sent to explore the thing died - violently - within minutes. Edward Hawks, Doctor of Science, was responsible for the first major breakthrough. He designed a matter transmitter that allowed each test subject to be duplicated - on the Moon. In theory, the man in the lab would continue to live after the death of his double in the structure. Unfortunately, the mental link between the two had proved too strong. So far, every volunteer had gone mad when his duplicate was killed - and the succession of tragedies was eating away at Hawks.