Within psychedelic culture the threat of the bad trip hovers like an ominous presence. Psychedelic or ‘Mind-clearing’ drugs may promise wisdom, visionary insight or a fabulous holiday for the brain, but they can also release the horrors of the id, tear the veil of sanity and pull you into the void. This class will chart the emergence of psychedelia across the Sixties and will examine the incorporation of its visual language in horror cinema during the period 1966-1972. Rather than seeing the films in question as acts of exploitation, the talk will frame them as radical works of acid horror, a from which in the case of The Dunwich Horror is used to conjure the cosmic vertigo integral to H. P. Lovecraft’s writing. Further, the talk will also read back from the films to the wider drug culture to uncover a sense of horror underpinning the psychedelic experience as a whole.