Everything matters

“Everything matters” names Hercule Poirot’s insistence that no detail should be dismissed merely because it appears small or inconvenient. It is both a practical rule of investigation and a test of a theory: when a fact will not fit, the detective must examine the gap and reconsider the explanation. In The Styles Case, that discipline turns apparently conclusive evidence against Alfred Inglethorp into a reason for doubt, and makes the overlooked medicine central to understanding Emily Inglethorp’s death.

The Rule and Its Method

Poirot describes investigation as a chain in which one fact leads to another. Each new detail must be tested against what has already been established; if it fits, the inquiry proceeds, but if something is missing or will not tally, the discrepancy must be examined rather than ignored. A detail that initially seems paltry may prove significant precisely because the current account cannot accommodate it.

He makes the rule emphatic: the detective courts confusion by deciding that a fact is too small to matter and forgetting it. In his formulation, evidence is not valuable only when its importance is immediately apparent. It must be retained long enough to be compared with other facts, and the theory—not the discordant fact—must give way when the two cannot be reconciled.

The method also depends on order and attention. Poirot praises Arthur Hastings for faithfully remembering and reporting details, while criticizing the order in which he presents them. The distinction is revealing: a witness may not know how to rank evidence, but the investigator must preserve it before deciding what it means. The rule opposes premature selection, not careful analysis.

Testing the Poisoning Theory

The principle enters the central question of how Emily Inglethorp received the strychnine. Poirot tells Hastings that the prevailing contention is that Emily died of strychnine poisoning, supposedly administered in her coffee, then asks when the coffee was served. The question redirects attention from the broad accusation to the timing and circumstances needed to test it.

The evidence against Alfred Inglethorp initially appears forceful. At the inquest, Albert Mace identifies him as the person to whom he sold the poison. Yet Poirot argues that the accusation is too conclusive: evidence that is unusually neat may have been manufactured, and the criminal’s effort to tighten the case against Alfred has made it vulnerable to one decisive cut. The rule therefore treats incriminating evidence as something to examine, not accept simply because it points clearly in one direction.

Poirot applies the same standard to Alfred’s absence from the house. Rather than treating it as straightforward proof of guilt, he says that if Alfred knew Emily would be poisoned that night, he would have arranged to be away; the contrived excuse leaves open two possibilities—that he knew what would happen or had another reason for being absent. The fact remains unresolved at that point. Its awkwardness requires further inquiry, not a convenient conclusion.

Contradictions and Reversals

Hastings calls a curious fact unimportant and suggests it need not be considered. Poirot objects that every fact must be taken into account and gives the rule its sharpest investigative form: if the fact will not fit the theory, let the theory go. This is more than an injunction to collect clues. It is a safeguard against the investigator’s attachment to a persuasive explanation.

The rule also shapes the interpretation of physical evidence. During John Cavendish’s trial, questions about objects found in an unlocked drawer expose a difficulty in the prosecution’s account: a person who had committed the crime would have had a week to remove or destroy the objects. The open drawer and the time elapsed do not themselves establish who placed them there, but they undermine the assumption that their presence proves John’s guilt. Handwriting experts likewise agree that the signature of Alfred Inglethorp in the poison register is not his, while allowing that it might be the prisoner’s writing cleverly counterfeited. The apparent clue thus remains open to competing explanations.

A related warning emerges when John questions Poirot’s account of Dr. Bauerstein’s demand for a post-mortem. John sees the demand as inconsistent with a plan to conceal poisoning as heart disease. The objection matters because it presses the explanation against an inconvenient action rather than treating the detective’s account as exempt from scrutiny. Across these reversals, “Everything matters” requires each theory to answer not only the evidence that supports it, but also the facts that resist it.

The Overlooked Link and Its Significance

Poirot’s reconstruction of Emily’s final hours gives the rule its fullest consequence. He interprets a damp, coffee-scented stain and small china fragments in her room as signs that a coffee cup was broken near a tilting table. In his account, Emily did not drink the coffee; she heated and drank her cocoa instead. Since he also concludes that the cocoa contained no strychnine, neither of the initially suspected drinks explains the poisoning.

The inquiry must therefore turn to a third medium: Emily’s medicine. Poirot says that the strychnine was already present in the mixture prescribed by Dr. Wilkins. The route to that conclusion depends on refusing to force the evidence into the initial coffee theory. An overlooked detail about what Emily actually drank changes the question, and the revised question exposes the medicine as the missing link.

Timing supplies the final turn. The tragedy had apparently been intended for Monday evening, when Emily’s bell wire had been cut and Cynthia was away overnight, leaving Emily isolated in the right wing. But Emily forgot her medicine while hurrying to a village entertainment, then lunched away from home the next day. The fatal dose was consequently taken twenty-four hours later than intended. Poirot identifies that delay as the reason he possesses the last proof: three pieces of a letter in the murderer’s handwriting, which he begins to read aloud.

The expression thus joins method to narrative structure. Facts first invite confidence, then become unstable when a new circumstance changes their meaning; the apparent strength of a clue may be evidence of deliberate fabrication, while a missed dose can determine when the final proof becomes available. Poirot’s rule does not make every detail equally significant in advance. It insists that none be discarded before the chain has been tested, because the detail that seems least important may be the one that completes it.