Having been guided through the Cliff's Edge Hotel by Pearl you will arrive at the entrance to Vault 118. Gain access to the Vault itself with your Pipboy. This will extend the bridge that allows access to the Vault itself. However you will be contacted by Maxwell, if you were not lead here by Pearl, to explain your purpose of coming into the Vault.
Waiting on the other side is Maxwell. This Mr Handy Unit helps with the management of the Vault and its inhabitants. He will explain, if Pearl did not earlier that there has been a murder inside the vault. The victim is Mr. Parker, the manager and financier of the Hotel.
You will be lead to the Theater. In there you will be able to talk to Maxwell more about the residences of the Vault. Asking about them being robots. Maxwell will explain they are Robobrains. They had decided to become Robobrains to wait out the effects of the Great War. Asking about where to start will prompt him to tell you to figure out how he died, then who had the means and motive to kill him. After that you will be prompted to confront the killer. Asking about the victim will have Maxwell tell you some about Ezra Parker's past. He had managed several venture projects around the world. He was the one who prompted several of the premier clients to invest into the Vault section of Cliff's Edge Hotel.