Lum gathers some sand on the flat rocks. He carefully flattens it, so as to create a smooth surface. Then he uses his knife's point to begin drawing sketches. He draws a series of maps for you to examine.
"We have scouted the prison and its buildings, to be prepared if the Empire's soldiers begin to cause trouble. I believe this knowledge will be of use to you."
He sketches a map of the southern territory. "There is a ridge, and then the land becomes wet and swampy in most places. They chose a foolish place to build their buildings; over time, the land has reclaimed much of it, and still they live there.
"There are three structures. This one, the most southern, is where most of the prisoners are kept. There are about a hundred now. It is also where the ship lands. You can see that most of the flattened rock-surface has been reclaimed by the swamp."
Lum draws another map. "This is where the prison guards live. It is much better kept, but as you can see there is a forest nearby. They keep vehicles there, including large walking beast-vehicles, that go about on two legs."
https://postimg.cc/image/p68uan4ol/
"It is this island here that I believe concerns you most." Lum draws a final map. "This is where the weapon that is supposed to attack enemy star-ships is. They test it from time to time; the light reaches the stars."
https://postimg.cc/image/6kaoa04it/
Lum sits back on his haunches, letting you look at his work.