E.C. Tubb 
Journey Into Terror 

The first exploratory expedition to Pluto returns with only one crewman aboard-the Captain, Jules Carmodine. There is a profound mystery as to what has happened to the original crew: Carmodine is suffering from an amnesiac block, and is broken in health-almost insane, and full of self-loathing.Medical treatment restores his health but the amnesia as to what had happened on Pluto remains. Carmodine is then forced to go back on a second expedition to Pluto to exorcise his tortured memories of abandoning his crew. And unless he can remember what happened, the second expedition will fall victim to whatever decimated the first. It is a journey he does not wish to make-a journey into terror!