London1864.OnaHackneyboundtrain,aguarddiscoversbloodinafirstclasscarriage-andabodyontherailwayembankment.Forthefirsttime,amurderhastakenplaceonBritain'srailways.Overahundredyearslater,thissingledocumentaryforBBCTwousesthefirsthandtestimonyofthepeopleinvolvedatthetimetoexplorethisuniqueeventandhowitprovokedahugepublicoutcryanddebate.
　　Thestoryquicklybecameanewssensationasthedangersofthebravenewworldofthetrainwerelaidbare.Overahundredyearslater,thewitnessestothisstorymaybelongdeadbuttheirwordssurviveincourttranscripts,memoirs,lettersandvividjournalism.Thesetestimoniesarenowusedtotellthestory,takingthedocumentarydeepintothenineteenthcenturytomeetanextraordinarycrosssectionofreal-lifeVictorianLondon-fromtheenginedriverwhofoundthebodytothedetectiveinchargeoftheinvestigation.WhokilledMrBriggs?