The Fearful Summons (Star Trek #74)

Captain Sulu of the U.S.S. Excelsior and his crew are kidnapped, and when negotiations lead nowhere, Captain Kirk and the other former officers of the Enterprise reunite to rescue their old comrade. The kidnappers, a little-known race called the Thraxians, prove more difficult to deal with than Kirk and his team had expected, for they demand powerful weapons in exchange for the hostages, and it seems that there’s no other way to save the Excelsior crew. But Kirk cannot give into their demands, since that would put countless other lives in danger, and violate the Prime Directive.