The Salt Castle: The Gardeners Episode 2

Once again, the rivalry between Apollo of Helios and his twin brother, Ares is spinning around Alex Clark. This time, the game turns deadly. Apollo has run afoul of the law on Uor, and Ares must capture or kill him in order to preserve the family’s wealth and power.
The conflict could have apocalyptic consequences on Earth as Ares tries to draw his brother from hiding. Each of the brothers controls a “Gardener”, powerful quantum devices that have walked the Earth in human form for over fifty thousand years. These machines can command any computer on Earth, including nuclear weapons systems. Ares has aligned himself with a secretive paramilitary group with plans to depopulate the Earth and remake it in the image of Uor. Apollo and Alex must stop them.