It is one of the most electrifying scenes in cinematic history.
In the dense jungles of the Amazon in the 16th century, a small group of Spanish conquistadors is picked out by the camera, struggling to make their way through fetid undergrowth on a delusional mission to find the lost city of El Dorado and the untold wealth it promises.
There's no CGI here. The film, Aguirre, The Wrath of God, was made in 1972 and the director, Werner Herzog, took his actors into the jungle for months, made them wear real armour, attempt to take real cannon and horses into impossible places and act under unbearable heat.
What you see on the screen is real agony and pain and breathtaking acting. There's too much Method here, even for Daniel Day-Lewis.
At the heart of the film is Aguirre himself, a mutinous lieutenant, who leads his men into the abyss and inevitable death.
The final scenes as, one by one, the men and women are killed by a hail of native arrows as they aimlessly drift down the mighty river on their makeshift raft is as exhilarating as the opening. No wonder Coppola was inspired by the film when he made Apocalypse Now.
It has been one of my favourite films for years. I've watched it scores of times, never tiring of hearing the distinctive Amazonian call of the Screaming Piha bird that fills the soundtrack and helps drive the party on to destruction.
But I haven't put it into the DVD for a while now. The trouble is Klaus Kinski, the actor who magnificently plays Aguirre and who in real life was as deranged as his characters.
It's no surprise that Herzog once genuinely put a gun to his fellow German's head and threatened to kill him, so tired of the man's antics on set was he.
But it was that lunacy, together with his swept white hair above angular face, bolting eyes and flaring nostrils, that made his cracked characters so compelling.
Now there's a different Kinski to contemplate. At the end of last year, daughter Pola revealed in a book that her father had sexually abused her from the age of five until she was a late teenager.
The allegations shocked Germany, where the actor is still revered, even though he has been dead for 20 years. My father, she says, "paid me to be his little sex-object, placed on silk cushions".
Suddenly, Kinski's derangement and well-chronicled obsession with sex became evil and tawdry. So now, in a world still reeling from Jimmy Savile's heinous crimes and the re-examination of our past popular history that has come with that, here is art house cinema's own version.
Those innocent young girls bopping self-consciously on Top of the Pops can never be watched for the simple joy of nostalgia again, for the pervert who loomed above them in the studio will always be there. Even some of the great songs (amid the dross) of that time have somehow become tainted.
Classical music has its own moral dilemmas, not least in the case of the great composer Benjamin Britten and his disquieting penchant for the company of teenage boys. This knowledge cannot help but seep into an evaluation of his music, can it?
So, can film-lovers still watch Aguirre without squirming? When the conquistador cradles his dying daughter on that raft in that magnificent finale, have we to now look away? Or does that fact that this film is Herzog's masterpiece, not Kinski's, save it?
That Kinski was merely a hired hand, a cipher through which the director told his brilliant story, could make a difference, couldn't it?
I'm not sure I know the answer. I suspect that resolution might lie somewhere in the need to downgrade the author, or the actor, in all art and allow the text to interact solely with ourselves and our own experiences.
What I do know is that the DVD is on the shelf unplayed and will remain so for a while yet.