Headscratchers / The Mysterious Affair at Styles

• How is Hastings not a suspect? Obviously he can't be for plot purposes, but in-universe it doesn't seem like he is ever even required to give evidence to anyone other than Poirot, which makes very little sense.
  • Extreme lack of motive, maybe?
  • Not everyone who happens to be at the scene of a crime is automatically promoted to "primary suspect to be viewed with unrelenting suspicion" status and remains that way permanently. Hastings barely has any knowledge or connection to the family and what's going on among them aside from a friendly acquaintance with one of them, he's been away fighting in the war until relatively recently (and so hasn't had time to develop any kind of motive), and it's not like he has any history of mental instability that would make it likely that he could be an impulse murderer or potential serial killer. Never mind Poirot, it would take even the dimmest junior constable about five minutes to realise that Hastings has absolutely no motive or reason to want anyone in that household dead, never mind the murder victim, and that he just happened to be in the wrong place at the wrong time on this one.
• What was in the letter from Mrs. Inglethorp to Evelyn Howard dated the 17th July - the true one that Ms. Howard suppressed and replaced with the date-tampered "can we not bury the hatchet" one from the 7th?
  • It's never revealed, so any response is almost certainly going to have to rely on Wild Mass Guessing to a degree. However, it's not unreasonable to suspect that, rather than a plea to burying the hatchet, it was actually expressing exact opposite sentiments along the lines of "Given what I've learned about you and Alfred, you're basically dead to me."

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