Octane (2003)

Divorced business-bitch Senga Wilson grudgingly drives daughter Nathalie 'Nat' home after a visit to her dad, far away. During a rest-stop, Nat sneaks out with a friend and joins a weird truck-nomadic hippie-like sort of cult, which Senga tails. Its 'father' uses drugs and sex to bind everyone to his bloodthirsty scheme. When Bradford PD detective Ned Stephens investigates, Nat's dad assures him she's safe with him and Senga is pathologically disturbed. Nightmares blur who is imagining or lying what.