Fletcher Reede is a fast-talking, career-focused attorney who relies on lying to win cases and navigate his personal life. He is recently divorced and often breaks promises to his young son, Max, due to his work commitments. Despite his affable nature, Fletcher’s constant deceit strains his relationship with Max and his ex-wife, Audrey. Frustrated by his father's broken promises, Max makes a birthday wish that his dad would be unable to lie for just one day. Miraculously, the wish comes true, and Fletcher finds himself living out a day where he cannot utter a single falsehood.

As Fletcher navigates his truth-bound day, he is forced to confront the web of lies he has spun in his professional and personal life. At work, the inability to bend the truth jeopardizes an important court case he is handling for a manipulative client involved in a contentious divorce. The truth-telling chaos ensues as Fletcher attempts to reconcile his career ambitions with the sudden demand for honesty, while also trying to repair his strained relationships with Max and Audrey. Throughout this extraordinary day, Fletcher embarks on a humorous and frantic journey of self-discovery that challenges him to reevaluate the importance of truth and integrity in his life.