From the Chaosium website:
A Call of Cthulhu Scenario of Darkness and Terror set in the Roaring 20s
This is a convention scenario with highly detailed characters and handouts intended for a theatrical style presentation in a single long session.
This adventure is intended for 4-6 players, and can be completed in a single 5-7 hour session. It is not a scenario for the squeamish keeper or players, and some may view the drama herein as harsh. The game begins on September 15, 1927.
Scene 1 – Opening the Door – 9:00 AM Thursday – September 15th
Most of the digging crew has been dismissed. The foreman, Harold Granby and two of his trusted crew remain above with a stock of crating materials.
The characters are gathered at the entrance to the vault. The tunnel is somewhat cramped and narrow. It is about 50 feet in length and extends down a flight of fieldstone steps from what was once the basement of an old house. Like a mining tunnel, it is shored up with strong wooden beams every few feet. At the end of the tunnel the characters face a solid granite door with a thick verdigris-covered copper ring. The door is rather plain and appears to have been marked with painted symbols that have been mostly worn away.
The scenario begins with the opening of the door.