Alice tilted her head, staring at the hologram map, and frowned.  "Or they have a mind-reader," she said - almost a joke, but not quite.  She took a step closer to the hologram, studying it.  "Or a really good psychic.  Of course, that would mean that nothing we do would remain a secret."

She glanced away from the hologram, to the men standing nearby, a thoughtful look on her face.  "If it's just a mole, it's dealt with easily enough.  Just don't tell them anything important from now on, and if anything on the display changes, then we know it's not one of them. Or, if you want it to be complicated, you could give each of the those thirty people a different job, and whichever one gets added to the map is our mole."  She sighed.  "That is, assuming this map gets updated, which it probably won't."

Alice fell silent, studying the map again.  She frowned as the map continued to rotate, and poked her finger at a spot.  "If those artifact smugglers go anywhere near my collection, I will be sorely displeased," she murmured, staring at the dot that was just about where her house was.