Rihannsu, Book 3.
The sword was the ultimate symbol of Romulan power, tradition, and pride. It lay in the Senate Chamber of the Romulan Star Empire, revered and untouched for centuries, until the day Dr. Leonard McCoy was tried for treason – and both were stolen during a daring attack on Romulus itself.
Now, to avenge that insult and save face in the eyes of their deadly enemies, the Empire must recover the sword at any cost. Their envoys to the Federation demand the return of the sword and the extradition of the Romulan renegades who aided the Starship Enterprise in McCoy's escape. If diplomacy fails, the Romulans will trap the Klingons and the Federation in open war.
In such dangerous times, the Starship Enterprise is assigned the most valuable – and volatile – element of all: the fugitive Ael, her stolen Bird-of-Prey Bloodwing, and the sword they carry. Ael will undoubtedly attempt to use ship and sword to foil her enemies and play her hand in the dangerous game that she's begun. But she will do it all under the watchful eyes of James T. Kirk, the Federation starship captain who knows her dangerously well...