Star Trek The Next Generation, book 40 : Possession
J.M. Dillard et Kathleen O'Malley1996

Eighty years ago, bodiless entities brought a plauge of violence and bloodshed to the planet Vulcan. The nigtmare only ended when the entities were trapped inside special containers.

Now, on the eve of a galaxy-scale scientific exposition, the containers have been opened, freeing the malevolent entities to possess the minds and bodies of all they encounter, including the crew of the Starship USS Enterprise-D. Friends turn into foes, and no one can be trusted, as Captain Picard faces a deadly and insidious threat. Unless the entities can be stopped once more, they will spread their madness throughout the entire Federation.