The first exploratory expedition to Pluto returns with the Captain, Jules Carmodine, alone ... What happened to the crew remains a mystery as Carmodine is suffering from amnesia, and mentally and physically broken in health. Later, although his health improves, the amnesia remains. Then, when Carmodine is forced to return to Pluto, he faces a journey into terror. He must remember what happened on that first mission - otherwise the second expedition will suffer exactly the same fate as the first.