Nightshade

Summary
From the back cover: After two hundred years of civil war the planet Oriana is dying. Most of the surface vegetation is gone, the air is nearly unbreathable, and the people themselves are dying. Now, the two warring factions have finally sat down to talk peace, and Captain Picard and the U.S.S. Enterprise are sent to help them negotiate a settlement.

Picard, Lt. Worf, and Counselor Troi beam down to Oriana, just as the Starship Enterprise is called away on another urgent mission. Alone on the planet, the U.S.S. Enterprise team learns that there are people that would rather finish the devastating conflict than talk peace. Suddenly, Picard is accused of murder and the delicate negotiations have fallen into the hands of Lt. Worf.

Now, Worf and Troi must unravel the truth and prevent planet-wide disaster, before time runs out for the people of Oriana and the crew of the Starship Enterprise.