Peregrine — Poul Anderson

There was Joachim, captain of the Nomad star ship Peregrine, and ruler of the Peregrine clan. There were also all the ship's officers and crew and their entire families. Bound to no world, the better part of their lives spent on the great ships, the Nomads were something like the gypsies who once roamed the lands of Earth, and something like the Vikings who once fared Earth's seas - but different from any human society known before.

Once a year, the captains of the Nomad ships met at their secret planet called Rendezvous, where the bylaws and intricate agreements of Nomad society were made and enforced. And this year, Peregrine Joachim had a bombshell to toss into the midst of his colleagues. Five Nomad ships had disappeared, vanished completely in an uninhabited area of space. It appeared to be no accident!