Exactlytwoyearsago,inBuenosAires,circumstancespreventedPoirotfrominvestigatingthesuddendeathofthebeautifulIrisRussell.Nowhehasthechancetotryagain,thistimeinLondon,whenayellowiris,mysteriouslyleftonhisdoorstep,alertsPoirotthatthekillermaystrikeoncemore.