The House of Evil by William Le Queux

It was a long time before Newcombe struggled back to convalescence; during that period Grewgus had several interviews with the doctor who was attending him, a young, harassed-looking man who had a large but not particularly remunerative practice in a poor neighbourhood. The detective came to the conclusion at their first meeting that he was not a very brilliant member of his profession. He said there were symptoms of poisoning, certainly, probably ptomaine poisoning. The landlady had said the patient told her he was dining at some restaurant the previous evening. Possibly some cheap one where there was little care exercised in the selection or cooking of food. Undoubtedly he had partaken of some dish which had produced this disastrous result.

Then came the day when Grewgus was permitted to go up to the ill-furnished room where the Colonial lay, a shadow of his former robust self. He stretched out a wasted hand. "Very good of you to come and see me, mate. My landlady told me a gent had been inquiring after me. For the life of me I couldn't guess who it was. I've no friends in this infernal country. And what made you look me up?"