London1864.OnaHackneyboundtrain,aguarddiscoversbloodinafirstclasscarriage-andabodyontherailwayembankment.Forthefirsttime,amurderhastakenplaceonBritain'srailways.Overahundredyearslater,thissingledocumentaryforBBCTwousesthefirsthandtestimonyofthepeopleinvolvedatthetimetoexplorethisuniqueeventandhowitprovokedahugepublicoutcryanddebate.