An Eye for an Eye by William le Queux

The discovery of the horror concealed within that closed room opened out an entirely fresh development of the mystery. On discussing it with Boyd after we had stealthily left the house we were in complete agreement that the dead man must have either been in hiding there, or else, being an imbecile, had been kept under restraint. The fact of the door being barred on the outside strengthened Boyd's belief in the latter theory, while I made the suggestion that he might have been imprisoned and died of starvation.

"No," Boyd answered, "I don't agree with you there, for it is quite plain that Lady Glaslyn must have been aware of his presence, and perhaps, indeed, arranged the room. There is every evidence that he was supplied with food at intervals, and cooked it himself, which shows that, even if an invalid, he was sufficiently active. My idea is that he may have been some relation whose demented condition her ladyship wished to keep from her friends and other members of the family, and that having died suddenly she was compelled to lock and seal the door, dreading the publicity of a coroner's inquiry, when the truth must have been made public."