One-time talented golfer, Wallace Avery (Colin Firth) is struggling with a life from which he longs to escape. Faking his own death, he acquires a forged passport and a new identity-that of a golfer named "Arthur Newman". "Arthur" heads out for Indiana to start a new life and a promise of a new job as a resident golf-pro at a prestigious club. Along the way, he meets the beautiful but troubled Charlotte (Emily Blunt), who is also traveling under a false identity-that of her schizophrenic twin sister, Michaela or "Mike"-and has fled her own home in North Carolina.

Arthur and Mike's relationship flourishes and they embark on an adventurous road-trip where they take a deviation, breaking into empty mansions and assuming other people's identities until, eventually, the role-playing games begin to lose their lustre, revealing two hearts hurt by life's challenges. Arthur & Mike are then forced to take another look at themselves and the real lives they've left behind.