Dave (Oyelowo) and Emma (Cuoco) have the seemingly perfect life - two kids, suburban house, good jobs - but they just want a little more fun. In fact, they need it. Looking to shake things up, they decide to ROLE PLAY. The rules are simple - they meet as strangers for one night to rekindle their relationship. While waiting for her "stranger" at a hotel bar in New York, Emma attracts the attention of a mysterious older man (Nighy), who stays to buy her and Dave drinks long into the night. 24 hours later, the man is found dead and a murder investigation is launched. Emma and Dave's role play game now becomes a case of mistaken identity that leads to Emma disappearing and Dave being questioned by the police for murder. As disguises unravel, David uncovers the unbelievable truth: his wife Emma is a professional assassin who has been living a double life for years.