chunk: Poirot clears Cavendish by proving it was Alfred Inglethorp who committed the crime, assisted by Evelyn Howard, who turns out to be his kissing cousin, not his enemy. The guilty pair poisoned Emily by adding a precipitating agent, bromide (obtained from Mrs Inglethorp's sleeping powder), to her regular evening medicine, causing its normally innocuous strychnine constituents to sink to the bottom of the bottle where they were finally consumed in a single, lethal dose. Their plan had been for Alfred Inglethorp to incriminate himself with false evidence, which could then be refuted at his trial. Once acquitted, due to double jeopardy, he could not be tried for the crime a second time should any genuine evidence against him be subsequently discovered. When he realized that Alfred wanted to be arrested, Poirot prevented it until all the evidence against him was at hand.