Amathematicianandauthor,LukeWilliams,istravellinguptoLondononatrainwhenhemeetsaoldlady,LaviniaFullerton,whoisalsogoingtoLondon,toScotlandYard.LaviniatellsLukethatinhersmallvillageseveralpeoplehavedied.ThelocalpolicearecertainthatitwasallaccidentalandaretakingnoactionbutLaviniaisn'tconvinced.InLondonLukewatches,horrified,asLaviniaisrunoverinahitandrunandhebecomesconvincedthatshewastellingthetruth.Hetravelsdowntothevillageandwiththeaidofalocalgirl,whoisalsoconvincedthatthedeathsweremurder,setsouttosolvethemystery.