Sobhraj evaded capture for some time and when he was incarcerated, managed to escape from prison several times. He was once the most wanted man on earth.
Callous and shocking though his crimes were, perhaps equally disturbing is the fact that he was aided and supported by his French-Canadian girlfriend, Marie-Andree Leclerc.
As in all television dramas, whilst based on facts and witness reports, much of what passed between Charles and Marie-Andree was speculative.
So was she a victim of adult grooming?
Around thirty when she met him on a holiday to Bangkok, Marie-Andree was not a gullible teenager. Sobrajh was very attentive and acted as a guide to the area. On her return to Canada, he love bombed her with letters and calls telling her he was in love with her and pleading with her to return.
Believing him to be sincere, she fell madly in love and went back to Bangkok.
Although Marie-Andree undoubtedly assisted Charles (who called himself Alain Gautier, amongst other identities) in drugging some of his victims, there is no evidence that she actually witnessed any of the murders and indeed, she claimed in court that she had no knowledge of them. No-one will ever know the truth for sure as Marie-Andree took it with her to the grave, dying of cancer at the age of 38.
However, their relationship bears many of the classic signs of narcissistic abuse, and the acting in this series is superbly convincing.
Initially, when she returned to Bangkok, Sobhrah withheld sex from her for a number a months, exerting control from the start. He continually made false promises: that they would marry, that she could have a baby, that they would move to Paris.
Needless to say, these never materialised, but he used them as a way to keep hooking her back. He even managed to justify his relationships with other women by saying he was just using them to help get the money they needed to set up home in Paris.
As their trail of destruction progressed, Sobhraj increasingly used threats and intimidation to keep Marie-Andree onside, fearing that she too would be sent to prison if she reported her concerns about him.
Although the crimes of Charles and Marie-Andree were horrific and extreme, the pattern of the relationship will be familiar to many of you who have been subjected to the grooming, domination and manipulation that is part and parcel of any toxic relationship.
I, for one, couldn’t help feeling a degree of sympathy for Marie-Andree Leclerc, along with the many millions of people who have unwittingly found themselves in too deep.
For support around adult grooming, please contact CAAGe
The Serpent is showing in the UK on BBC 1, Sundays at 9PM