The Brains of Earth
Reviewed date: 2012 Jun 18
This is a fun little book. What if every human being's brain was hosting a parasitic creature called a nopal? The nopals exist in a quasi-parallel, psionic plane of existence--a plane the nopals prevent their hosts from perceiving.
On the faraway planet of Ixax, the Xaxans have just emerged from a devastating civil war. The Tauptu (those free from nopal control) have defeated the Chitumih (those controlled by nopals). Having eradicated nopals on Ixax, the Xaxans turn to the rest of the galaxy: they wish to kill all nopals everywhere--starting with Earth.
Removing a nopal by force has the unfortunate propensity to kill the host, though. The only way around this is a torture device called the denopalizer. It causes specific, excruciating forms of pain which overwhelms the host's brain and persuades the nopal to let go. The Xaxans kidnap a scientist, Paul Burke, and enlist him to built a denopalizer and begin purging humanity.
But Burke smells a rat: why are the Xaxans in such a hurry? Why are they so unwilling to explore other kinds of denopalizers (perhaps ones that don't involve torture?) Why do they hate nopals so much? And parts of the Xaxan story don't add up. Are the nopals even real?
Burke manages to tune his mind to see into the psionic realm, and makes a startling discovery. The nopals are real, yes. But equally as real, and more dangerous, is the gher, a creature that is controlling the minds of the Xaxans. It turns out that the nopals, relatively benign in themselves, prevent the gher from controlling the minds of the host.
Burke protects his mind using a helmet made from a dead nopal, which blocks the gher. Then he commandeers the Xaxans' spaceship and locates the homeworld of the gher. He kills the gher.