Just as she is recovering from a breakdown, Anna's world is rocked when her younger sister gets engaged. She teams up with the alcoholic best man to break up the engagement, convinced they are trying to save her sister, his best friend, and themselves from a lifetime of misery.

When the 1989 "one-hit-wonder" glam-metal band "Sonic Grave" embark on a trip to Coachella in hopes of a comeback, their peyote trip pit stop in Joshua Tree incites an "unworldly" viscous attack, and they must "rock" themselves out of harms way.