Agatha Christie: And Then There Were None/Chapter 1

After the intro you stand on the patio of the mansion, with Thomas Rogers, the butler standing behind you. Go forward and follow the path until you reach the pier. Take a look at the scuttled boat and and make your way back to the mansion. On your way back you can take a side path to your left and meet Mr. Marston. After talking to him head back to the patio. Talking with Mr. Rogers and he will let you into the house.

Kitchen
After Mr. Rogers leaves you follow him to the kitchen. You'll see a cutscene where Ethel Rogers complains about the situation and leaves then. Go forward and exit the kitchen. On the back hall take the door to the right to enter the Rogers' room.