The mystery of the 'nightmare syndrome'

In 1981, an American doctor, Larry Lewman, uncovered a mysterious pattern of sudden, nighttime deaths in refugees from Southeast Asia.

Dr Lewman, a medical examiner for the Oregon State Police, first saw something was wrong after examining the body of a 29-year-old man, who had died suddenly and without apparent explanation. According to the police report, the man had died in his sleep, but the doctor was unable to find any underlying condition or cause for the abrupt death.

Then, just three days later another body of a young man who had also died in his sleep was brought in to his mortuary. The man's wife told Dr Lewman that she was woken by his loud panicked breathing, which she thought was a nightmare.

She told Dr Lewman that she had tried to wake him up but discovered that he was already dead. Dr Lewman contacted the coroner's offices and forensic scientists across the United States after he became aware of an increasingly disturbing pattern of sudden nighttime deaths among at least 100 male refugees from Southeast Asia.

All had arrived in the US during the late seventies and early eighties, and many had mysteriously died in their sleep.

Find out what happened next in the film above