For the first three-quarters of this film, it's a surrealist comedy about a bunch of Vietnam crazies, with some truly bizarre ideas and some absolutely excellent performances from Stacey Keach, Scott Wilson and a particularly stern Neville Brand as Major Groper, the 'Straight Man' lost in the asylum.
Then, just as you're settling into the madness, there's a shift from screwy comedy to a totally different fable of sacrifice and redemption, in which Killer Kane can bring death to redeem rather than just to destroy.
In truth, this sea-change is one of the reasons why it has become a forgotten gem, as it's so difficult to categorise, and for many the change in tone sits uncomfortably with the whimsy, slapstick and throwaway one-liners of earlier in the film. I, however, feel that there is a dark undercurrent all the way through, and the final confrontation between Kane and the Hell's Angels is a reflection of the madness within the asylum to that within society.
And the end - well, it just fills me with hope and belief in humanity every time I watch it.
Do watch this film - it should not remain a forgotten gem!