The Borg have found a secret passage through subspace and are using it to attack the Federation. But the passage is only one of many that the Enterprise crew have discovered inside a nebula. Working together, Captains Picard and Dax must find the right one before they can lead a counterstrike to stop the Borg invasion. Meanwhile, Captain Riker and the crew of the Titanare being held hostage by the powerful reclusive aliens know as the Caeliar. Their freedom hinges of the action of fellow-prisoner Erica Hernandez, commander of the long-lost starship Columbia. Hernandez has lived among the Caeliar for centuries, enduring disasters, accidental time travel and interstellar exiles. After so long, can she be persuaded to fight for her freedom, or is it too late for the Titanas well as for her?