The Peacekeepers (Star Trek The Next Generation, No 2)

Exploring a deserted alien spaceship, Lt. Commander Data and Lt. Geordi LaForge suddenly find themselves transported light-years away -- into the middle of a deadly conflict!

While Captain Picard and the crew of the U.S.S. Enterprise™ search feverishly for the missing crewmen, Data and LaForge discover they are in a station almost identical to the one they were exploring, high in orbit around an earth-type world. Years before, the occupants of that planet accidentally stumbled onto the ship and its advanced technology -- and since then have used its weapons to keep the nations on the planet below disarmed, and at peace.

Now their own arrival has precipitated a crisis on the station. Somehow, data and LaForge must find a way to restore trust between the planet below and the station's guardians up above -- before a final, destructive war breaks out!