Miss Howard had always seemed to me so essentially honest ”almost uncomfortably so. Poirot gave me a curious look, which I could not quite fathom. 
Miss Howard seems overly dishonest and Poirot gave me an approving look.
mnli hypothesis: Miss Howard seems overly dishonest and Poirot gave me an approving look. premise: Miss Howard had always seemed to me so essentially honest ”almost uncomfortably so. Poirot gave me a curious look, which I could not quite fathom. 