Secret Agent OSS 117, Colonel Hubert Bonisseur de La Bath (Kerwin Mathews) is sent to Thailand following the murder of OSS agent Christopher Lemmon. Lemmon had been investigating the break out of Plague (disease) epidemics in India following health workers inoculating the locals to protect them from cholera. Lemmon had discovered that the medicine made in Hogby Laboratories in Bangkok had been switched with plague germs infecting the population with fatal results.