Straight-laced shrink Romain is fascinated by his new psych ward patient Léo Milan, who claims to be a highly-trained international spy, code-named “The Lion”. But of course, that’s just crazy talk, right? Maybe not. When Romain’s fiancée is kidnapped before his very eyes, just as The Lion predicted, Romain realizes that Léo is the only one who seems to know what’s going on. And only he has the skills to rescue her. Desperate, Romain breaks out The Lion and does his best to keep up with him, in a frantic chase across Paris to rescue Louise and protect France’s central bank from the heist of the century.