Nightshade - Laurell K Hamilton

After two hundred years of civil war, the planet Oriana is dying. Most of the suface vegetation is gone, the air is almost unbreathable and the population is on the verge of extinction. Now the two warring factions have finally sat down to talk peace, and Captain Picard and the USS Enterprise are sent to help them negotiate a settlement.
Picard, Lieutenant Worf and Counselor Troi beam down to Oriana, just as the Starship Enterprise is called away on anothe urgent mission. Alone on the planet, the USS Enterprise team learns that there are people who would rather finish the devastating conflict than talk peace. When Picard is accused of murder, the delicate negotiations fall into the hands of Lieutenant Worf. Together, Worf and Troi must unravel the truth to prevent planet-wide disaster before time runs out for the people of Oriana and the crew of the Starship Enterprise.