Set primarily in 1975 and 1976, *The Serpent* chronicles the chilling true crimes of French-Vietnamese serial killer Charles Sobhraj, who preys on Western hippies traveling the "Hippie Trail" through
Southeast Asia. Operating under the alias Alain Gautier, Sobhraj lives a life of deceptive luxury in Bangkok alongside his devoted French-Canadian partner, Marie-Andrée Leclerc, whom he manipulates into blind compliance. Sobhraj’s primary motivation is greed and control; posing as a wealthy gemstone dealer and friendly expatriate, he drugs, robs, and murders vulnerable backpackers who trust him completely, stealing their passports and money to finance his lavish lifestyle. He is aided by Ajay Chowdhury, a volatile and desperate Indian immigrant who acts as his loyal enforcer and reluctant executioner.The central dramatic conflict ignites when Herman Knippenberg, a junior Dutch diplomat in Bangkok, stumbles upon the disappearance of two young Dutch travelers, Henricus Bintjes and Domitien De Ruiter. Driven by an obsessive sense of justice and moral duty, Knippenberg launches an unauthorized, grueling investigation that quickly uncovers a horrific pattern of drugged victims, forged identities, and burnt bodies. Despite facing constant bureaucratic obstruction from indifferent embassy superiors and local police who dismiss missing foreigners, Knippenberg perseveres, slowly building a damning case. He forms a crucial alliance with Paul Siemons, a neighboring Belgian diplomat, and later receives vital insider information from Nadine and Remi Gires, French expats who live in the same apartment building as Sobhraj and gradually realize they are harboring a monster.As the net closes, Sobhraj’s paranoia escalates, leading him to poison and murder an array of tourists, including American backpacker Teresa Knowlton and French traveler Vitali Hakim, while expertly evading local law enforcement through bribes and forged documents. The tension peaks when Sobhraj and Leclerc brazenly travel back to Thailand despite international warrants, believing they are untouchable. Knippenberg finally manages to convince Thai authorities to raid Sobhraj’s residence, leading to the dramatic arrest of Charles, Leclerc, and Ajay. However, true justice proves elusive in the immediate aftermath; through bribery and manipulation, Sobhraj manages to secure his eventual
release from prison years later, leading to a frantic global manhunt. Ultimately, decades later, Knippenberg’s relentless crusade culminates in Sobhraj's final capture in Nepal, bringing a haunting end to the reign of the cunning, charismatic psychopath who ruthlessly exploited the innocence of the open-minded generation.