The Railway Killers S01E02 - Episode 2

A woman goes missing while on a train home from work, immediately stoking fears that the killers have struck again - fears that prove accurate when her body is discovered. The police painstakingly work through a list of more than 3000 potential suspects with blood that matches the earlier crime scenes - and eventually come across a man whose suspicious behaviour and similarity to the rape victims' descriptions marks him out as a possible perpetrator.