Spider is set in the East End London in the 1960s and '80's. A deeply disturbed boy, Spider, 'sees' his father brutally murder his mother and replace her with a prostitute, Yvonne. Convinced they plan to murder him next, Spider hatches an insane plan, which he carries through to tragic effect. Years later, Spider is released into a halfway house, where he receives little care or attention from the landlady Mrs. Wilkinson. Unsupervised, Spider stops taking his medication and starts revisiting his childhood haunts. His attempts to sustain his delusional account of his past begin to unravel and Spider spirals into fresh madness.