He attacked her before evading capture
Story
Delia Balmer, an agency nurse, met Sweeney, who confessed to killing his ex-girlfriend.
Based on a true crime story
Balmer rebuilt her life to confront Sweeney seven years later after he was arrested for another murder..
The bodies were dumped in canals in Rotterdam (not Amsterdam) and London
Not only is this a compelling, uncomfortable drama, one almost unique in not seeking to exploit misogynistic violence for kicks, but also an indictment of a judicial system where everyone involved is clearly compromised by seeing the victim as a means to their end career-wise.
The viewer is also forced to confront their expectations of a true-crime victim
The police want a conviction and the criminal is the target and the victim is merely the enabling ammunition to achieve this; a passive cipher best forgotten afterwards unless they become useful again.
Delia Balmer/Anna Maxwell Martin does not bow to this convention and the syrup-free drama is all the better for presenting a victim in the round
Typically these are vulnerable and quite passive individuals lacking confidence and not infrequently conventionally attractive as film and television producers seek to manipulate empathy from their audiences by all means at their disposal.