The great sphinx of 60s garage rock, Roky Erickson helped launch the psychedelic era with the clangorous 13th Floor Elevators but soon became a notorious acid casualty. After copping an insanity plea in a drug case he spent three years in a Texas state mental hospital, and for the next 30 years his life was an overgrown forest of schizophrenic behavior. This absorbing documentary by rock journalist Keven McAlester is framed by the legal battle that Sumner Erickson, the singer’s younger brother, waged in 2001 to wrest custody of Roky from their aging and eccentric mother, Evelyn. Friends and family tell the story of Roky’s troubled life, and as McAlester gets closer to Evelyn, disturbing details about the Ericksons begin to emerge. I came to this expecting a standard rock doc, but its cobwebbed tale of an aged parent and grown child’s debilitating relationship seems closer to Grey Gardens. 92 min.