Surface (Not Shown)
You'll find four dark elf nobles standing over the body of Professor James. They won't be happy to see you, but if you bluff and say you're an archeologist with a different viewpoint than Professor James, and that you'll tell everybody what happened to Professor James, they'll leave you be. Then you can enter the ruins and do whatever you want inside. If the conversation doesn't go well for you, just don't rat out Cassandra Pettibone or else you'll botch the funerary stone quest. The dark elf nobles aren't very difficult to kill.
If you have the Conjure Spirit spell, you can conjure Professor James' spirit. Then he'll tell you that the elves attacked without warning and slaughtered everybody.
1 - Funerary Stone
This is the stone Cassandra Pettibone wants. It's pretty big (6x4) so you'll probably need to create room for it.
2 - Treasure Chest / Barrel
The treasure barrel to the south always contains a medallion of silence.
A. Exit back to the world map.