Threshold, the second feature from co-directors Powell Robinson and Patrick R Young, following their debut Bastard (2015), was improvised and shot on two iPhones over the course of a 12-day road trip with a crew of just three. The result is an inventive and compelling psychological thriller with hints of the supernatural that recalls such indie cult classics as Ben Wheatley’s Kill List (2011) and Justin Benson And Aaron Moorhead’s Resolution (2013).