Star Trek The Next Generation, book 27 : Guises of MindRebecca Neason1993

The world Capulon IV is finally ready to join the Federation after years of waiting. All that remains is the ruler's coronation and a routine signing of the final treaty. When the crew of the USS Enterprise and their passengers – a group of women from a religious order dedicated to helping the downtrodden – arrive for the event they expect to find a world willing and happy to receive them. Instead, they encounter deceit and treachery. The crown prince, once excited and eager to join the Federation, now refuses even to speak with Captain Picard.

Beaming to the surface in an attempt to work out the problem, Picard, Troi, and Mother Veronica, the abbess of the nuns, are drugged and captured. Now they must somehow escape and stop the crowning. If they cannot prevent it, the King will be omnipotent, with the power to destroy the Starship Enterprise and all of Capulon IV as well...