Mutability On Mars

Fuller, and Dr. Adela Rodgers are on a mission to explore strange phenomena near the "Face" of Cydonia, a large geological feature on Mars. They find remnants of an old Russian probe, and the spacesuits of cosmonauts, from which skulls emerge. The skulls travel to Earth and cause havoc, sucking out the skulls of ordinary people and absorbing them into a huge skull entity. Fuller and Adela return to Mars where they find a Bird Martian who says he alone can defeat the skull entity. The Bird Martian travels to Earth and fights a psychic energy battle with the skull entity, and miniaturises the huge skull, then crushes it. Other strange things happen and the Space Council back on Earth decide to nuke the base on Mars and the area around the "Face". Fuller and Adela are trapped as their bus crashes before they can reach the shuttle. They die in the thermonuclear explosion, but find their existence has not ended and they are now spirits. The Bird Martian re-appears and tells them their survival is due to "mutability on Mars", where organic human life can change into a spirit form, and potentially, anything can be transmuted into something else.