Two years ago, Edgar Tang was driving with his radio tuned to the BBC.
He heard a documentary about a man infected with HIV, the virus that causes Aids.
After a series of radical medical interventions in 2009, the man found himself clear of the virus.
For all practical purposes, he had been cured of the HIV infection, the first person in the history of the disease to have that outcome.
Tang, now 38, was transfixed.
This mysterious and very lucky survivor, an American living in Germany at the time, would be called The Berlin Patient, after the city in which he received the stem-cell treatments that would clear him of the disease.
That fascination would result in the documentary I Hugged The Berlin Patient, which opens tomorrow at the Cathay Cineplex Cineleisure Orchard.
As Tang says in the film he co-directed, the patient, whose real name is Timothy Ray Brown, was "an underdog you want to cheer, an outsider.
Suddenly he is thrust into a world where he is put on a pedestal, to become the chosen one.
He never guessed he would be this special person, the first person to have been cured of HIV".
Speaking to Life!, he says that the idea for making a documentary about his search for Brown came about by chance.
"I had a month to spare from work. I didn't think about doing a documentary. I thought I would go to Berlin and get inspired by his life to write a fictional feature about his experience."