Judas Valley, The by SILVERBERG, Robert and GARRETT, Randall

Why did everybody step off the ship in this strange valley and promptly drop dead? How could a well-equipped corps of tough spacemen become a field of rotting skeletons in this quiet world of peace and contentment? It was a mystery Peter and Sherri had to solve. If they could live long enough! [from the Judas Valley] Originally published in Amazing Stories October 1956.