Robert Pattinson as Constantine "Connie" Nikas,[3] Nick's older brother and Corey's boyfriend Ben Safdie as Nickolas "Nick" Nikas, Connie's younger, mentally-handicapped brother Jennifer Jason Leigh as Corey, Connie's girlfriend Barkhad Abdi as Dash, a security guard working a night shift at an amusement park Buddy Duress as Ray, a criminal whom Connie mistakes for his brother Taliah Webster as Crystal, a teenage girl who helps Connie Necro as Caliph, a criminal friend of Ray Peter Verby as Peter, Nick's psychiatrist