What do Charles and Andrew find in the 400s room?

When they step inside the room, it is dark and smells of pine trees. A voice greets them from the ceiling speakers. Spotlights thump on and Charles and Andrew see a row of four featureless mannequins. One of the mannequins tells them they can watch a film while their family trees are researched. After watching the film, the two boys listen to their ancestors' stories. Through one of the stories, Charles believes he has gotten a bonus clue.