The Mote in God's Eye

In 3016, the 2nd Empire of Man spans hundreds of star systems, thanks to the faster-than-light Alderson Drive. Intelligent beings are finally discovered at the Mote, an isolated star in a thick dust cloud. This bottled-up ancient civilization, at least one million years old, is welcoming, kind, yet evasive, and has a dark problem it has not solved in over a million years.