Star Trek: The Next Generation: Stargazer: Enigma

Without warning, a Starfleet ship is overwhelmed by a mysterious, alien aggressor—one who appears to possess an intimate knowledge of the vessel''s tactical technology. Then a second Starfleet ship is attacked. And a third.

Twenty-eight-year-old Jean-Luc Picard, captain of the U.S.S. Stargazer—a Constellation-class starship—is ordered to help form a desperate line of defense against the aggressor. ...