Sam is a struggling but loving single mother who hides a dark secret: she is addicted to online gambling. With her ex-husband threatening to take custody of their children and debt collectors knocking at the door, Sam discovers that she could have a way of turning her luck around. As an after-hours cleaner in a corporate London office, she is unknowingly given access to potentially lucrative stock market information which she uses to enter the dark world of insider trading, with the help of her best friend Jess.