On the last day of September 1980, my eight friends and I were walking down a high ridge and, a little before noon, we reached the upper course of the Kha Khaeng stream. Monsoon rains had been falling for days on end, at times seeming to split the whole range asunder, at others melting in a fine drizzle that lasted from dawn to dusk. Even when the rain stopped, the whole jungle was still as dim and damp as a deserted theatre. The smell of old leaves and soggy rotting logs had filled our nostrils along the way.