Boek Star Trek the Next Generation Masks (John Vorholt)

The USS Enterprise-D journeys to Lorca, a beautiful world with a feudal culture where the inhabitants wear masks to show their rank and station. There, Captain Picard and an away team don masks of their own to begin a quest for the planet's ruler and the great Wisdom Mask that the leader traditionally wears. Their mission: to establish diplomatic relations.

But shortly after transporting, Picard and his party lose contact with the ship, and Commander Riker leads a search party down to the planet to find them.

Both men, however, are unaware that their searches – indeed, the ship's entire mission – are part of a madman's plan. A madman who is setting the stage for a trap that will ensnare both the Enterprise landing parties, and leave him poised to seize control of the awesome Wisdom Mask…

And the planet Lorca itself