Chap­ter XII begins with a sense of ris­ing antic­i­pa­tion as Poirot returns to Styles accom­pa­nied by Japp and Sum­mer­haye, ready to lay bare the tan­gled truths behind Mrs. Inglethorp’s mur­der. The pres­ence of the detec­tives sig­nals that a break­through has been reached, and Poirot wastes no time in sum­mon­ing the house­hold for the final expla­na­tion. Mary Cavendish allows the gath­er­ing to pro­ceed, her calm demeanor reveal­ing a silent con­fi­dence in Poirot’s abil­i­ty to see jus­tice through. Each mem­ber of the house­hold enters the salon with their own unspo­ken anx­i­eties, yet it is clear that the veil of uncer­tain­ty is about to be lift­ed. Poirot stands not just as a detec­tive but as the orches­tra­tor of clar­i­ty amid chaos, ready to untie every knot of con­fu­sion with log­ic and insight. The room, filled with ten­sion and antic­i­pa­tion, mir­rors the grav­i­ty of what is about to unfold.

Poirot’s method­i­cal approach starts with a foren­sic dis­sec­tion of the crime scene, where seem­ing­ly minor details become the foun­da­tion of his argu­ment. He points to the stained car­pet and a torn fab­ric thread, estab­lish­ing that some­one had indeed entered the room when the door appeared to be locked. This chal­lenges the ini­tial time­line and repo­si­tions the viewer’s under­stand­ing of how the night unfold­ed. He notes how con­fu­sion arose around a locked door that, in fact, was nev­er tru­ly secure, unrav­el­ing the assump­tion that no one could have reached Mrs. Inglethorp. The atten­tion he gives to the bro­mide box and the way med­i­cines were arranged shows the lev­el of detail required to under­stand the mur­der method. In each state­ment, Poirot tight­ens the thread, slow­ly reveal­ing how evi­dence long thought irrel­e­vant actu­al­ly formed the core of the case.

Atten­tion soon shifts to the will, that piv­otal doc­u­ment which Mrs. Inglethorp had recent­ly altered but which could not be found. Poirot the­o­rizes that she, per­haps in a moment of clar­i­ty or con­fu­sion, destroyed her own will—an act that bore great con­se­quence. The deci­sion to light a fire dur­ing a warm evening raised eye­brows, but Poirot reads it as a pan­icked attempt to remove evi­dence before her death. The destruc­tion of this doc­u­ment adds urgency and des­per­a­tion to the scene, mak­ing clear that Mrs. Inglethorp had feared some­thing, or some­one. Her motives, and the pres­sure she felt in those final hours, sug­gest that she was aware of dan­ger. In this moment, Poirot empha­sizes how the crime was not just a spon­ta­neous act but built on emo­tion­al manip­u­la­tion and long-brew­ing resent­ment.

Poirot dis­miss­es the pop­u­lar the­o­ry that the poi­son was deliv­ered through cof­fee. Instead, he redi­rects the dis­cus­sion toward the med­i­cines on Mrs. Inglethorp’s shelf—common house­hold treat­ments, famil­iar yet dan­ger­ous when tam­pered with. The poi­son, he argues, was admin­is­tered through a sub­sti­tu­tion, not an addi­tion, reveal­ing a far more cun­ning plan than orig­i­nal­ly believed. The mur­der­er had relied on famil­iar­i­ty and rou­tine to car­ry out the plan with­out arous­ing sus­pi­cion. By sub­vert­ing what seemed nor­mal, the killer cre­at­ed con­fu­sion that only a metic­u­lous observ­er could untan­gle. In this sub­tle shift, Poirot under­scores how dan­ger often hides in plain sight.

As Poirot walks the audi­ence through the series of decep­tions, a pic­ture emerges not just of one crime but of a house­hold rid­dled with secrets. His insights into Mary Cavendish’s role are espe­cial­ly poignant, show­ing how inno­cence can be mis­tak­en for guilt when emo­tions and assump­tions cloud judg­ment. The locked door, the faint foot­prints, and the con­fused tes­ti­mo­ny all fall into place under Poirot’s guid­ance. He does not mere­ly accuse; he explains, bring­ing under­stand­ing to both the guilty and the mis­led. Mary’s name is qui­et­ly cleared, and with that, one lay­er of the household’s ten­sion dis­solves. Her relief is felt not only by her but by the audi­ence, who have watched her teeter on the edge of sus­pi­cion.

The cul­mi­na­tion of Poirot’s deduc­tions leads to the dra­mat­ic reveal of the true mur­der­er, sup­port­ed by phys­i­cal proof and the unrav­el­ing of motive. A forged sig­na­ture, a changed rou­tine, and the manip­u­la­tion of rela­tion­ships are all exposed. The motive—greed cloaked in affection—reflects the painful real­i­ty that trust was betrayed in the worst way. In clas­sic Poirot fash­ion, the evi­dence is so thor­ough­ly laid out that no argu­ment can stand against it. The truth, once scat­tered in frag­ments, now stands whole. Styles, once dark­ened by mys­tery and mis­trust, sees light return through the order that Poirot restores. His tri­umph is not in accu­sa­tion, but in resolution—offering the house­hold peace after so many days of doubt.