You were told there would be a door.

There is. Below is the last plan of Halmerton House on the night everything ended. Five guests, five statements. Four of the rooms held someone. One room held nobody. Solve it, walk through the door and go to the solution.

What the five of them said

Mr Cole stood in the north-east corner of the house.
Lady Fenwick was in the library, in the westernmost column.
Dr Hallam was the only one in the hall.
Miss Ashby and Colonel Prewitt were both in the kitchen, the Colonel the further west of the two.
The Colonel stood in the southernmost row.

Which room was empty?

One word. If the house has no such room, you will be told so.