Interphase, Part 1 (Star Trek: S.C.E., #4)

STARFLEET CORPS OF ENGINEERS
More than a century ago, the U.S.S. Defiant ™ disappeared with all hands into an interspatial rift deep in Tholian territory. Now the derelict ship has been seen drifting in and out of ordinary space, and the Tholian authorities have reluctantly agreed to let Starfleet retrieve the Defiant from the rift. Perhaps, at long last, the lost ship can be brought home and its valiant crew paid their final respects.
Captain David Gold and an S.C.E. team from the U.S.S. da Vinci succeed in boarding the Defiant, but their investigation soon uncovers a dangerous secret. For more than a hundred years, an ancient super-weapon has been hidden away within the scarred and lifeless starship, along with evidence of a long-forgotten atrocity -- evidence that could ignite a vast interstellar war!