Taking Wing (Star Trek: Titan, Book 1);

In the wake of the assassination of the Romulan Senate and the chaos and power struggles that threaten to destroy the Romulan Star Empire, Captain William Riker and the U.S.S. Titan head to Romulus to set up negotiations among the powerful factions, unaware that remnants of the Tal Shiar, the notorious Romulan intelligence service, are threatening to unleash a bloodbath. Original.