The Fleet Of Stars

Poul Anderson's The Fleet Of Stars, "Harvest Of Stars" Tetralogy Vol IV, is the first real sequel to Harvest Of Stars, Vol I. Its action begins not back in the Solar System during the later events of Harvest Of Stars but in the system of Beta Hydri which, like two other planetary systems, has been colonised from Alpha Centauri considerably later.

On the one hand, the continuing characters, whether downloaded into artificial neural networks or re-incarnated in newly grown human bodies, have moved even further away from Earth. On the other hand, there are first hints of interstellar interaction. A laser message beamed from Proserpina to the Lunarians at Alpha Centauri and relayed to Beta Hydri informs the colonists that the cybercosm on Earth:

may be suppressing data from a solar gravitational lens;
may have sabotaged a Proserpinan lens;
had stopped antimatter production on Mercury as no longer needed by the stabilised Earth-Luna economy;
but has restarted production, possibly to power interstellar craft (the Proserpinans have detected signs of such craft leaving and entering the Solar System).

The incarnate Anson Guthrie of Beta Hydri IV reflects further that the cybercosm may be spying on the extra-solar colonies with mini-robots and would be able to plant cybercosms in the galaxy faster than organic life can proliferate on an interstellar scale. The scene is set for a potentially galactic conflict albeit at sublight speeds. Guthrie has been working on a shipyard project while his partner visits one of their sons, his wife and children on another continent but a download Guthrie will now travel to Sol via Alpha Centauri to investigate.

Of course, this moves the story back to the Solar System after all but, meanwhile, the action has definitely progressed beyond the end of Harvest Of Stars. We are no longer reading of events that are contemporaneous with any that were described in a previous volume. Onward.