Based on a true story, Charles Sobhraj was dubbed 'The Serpent' due to his conniving ways and constant escape from reprimand. He was also nicknamed the 'Bikini Killer' due to the clothing worn by his victims.
Production in Thailand was shut down for 5 months due to the Covid 19 pandemic. Filming was originally planned to resume in Budapest but transferred to Tring, Hertfordshire in the UK.
Jenna Coleman nearly turned down the role of Marie-Andrée Leclerc suggesting a French actress be cast instead.
Jenna Coleman was asked to audition in French, a language she doesn't speak. She had to learn phonetically.
Foufou, who plays Frankie the dog, was a troublemaker onset and kept breaking things in his path. One day the cast noticed he was calm and quiet. What the producers didn't tell anyone is they replaced Foufou with another dog.