Full Circle by Alfred Taylor
Millions of years ago an alien race sent seed pods out into space to replace any intelligent life in the Galaxy with their own. In 1861, Earth’s only defense is Mark Aaron, an android who came from the year 2372 to preserve history from a temporal terrorist. Mark, and his android wife Jane, must travel to the Galactic Core to save a peaceful alien civilization from annihilation by solving the mystery of its past. Then, they travel to London to intercept the seed pod and prevent a similar invasion on Earth. What should have been a simple retrieval becomes a desperate search which ends in robbery and murder.