Olivia Barron is a dedicated college student who consistently prioritizes the needs of others above her own. As she plans to spend her spring break constructing houses with Habitat for Humanity, her best friend, Markie Cameron, persuades her to instead join their group of friends for a trip to Mexico. While at a bar, Olivia encounters a mysterious man named Carter, who invites the gang to an abandoned church for a night of revelry. Once there, Carter introduces a game of truth or dare, revealing that it has a dark twist. With their friend Tyson Curran disclosing Olivia's hidden crush on Lucas Moreno, Markie's boyfriend, the game spirals into chaos when Carter alerts them that they are playing a deadly version. He warns that failing to comply with the game's challenges could cost them their lives.
Back at school, Olivia begins to experience unsettling hallucinations urging her to decide between truth or dare. She chooses "truth," unwittingly exposing Markie's history of infidelity with Lucas. As the stakes escalate, they learn of a tragic incident involving their friend Ronnie, who was compelled to take his own life after neglecting a dare. When Lucas opts for "truth," he confesses his feelings for Olivia, igniting a rift within the group. Under the game’s pressure, Markie breaks Olivia's hand, while their closeted friend Brad Chang faces the difficult task of coming out to his father.
As the group grapples with the horrifying game's consequences, Tyson, still in disbelief, meets a tragic end after lying. Their search for answers leads them to a chilling online story about Giselle Hammond, a woman who once set a girl on fire while engaged in the game. When they secure a meeting with Giselle through social media, she unveils that her friend, Sam Meehan, once drunkenly vandalized the church, unleashing the cursed game that claimed her friends. It becomes clear that Giselle has been forced to target Olivia, resulting in a heartbreaking sacrifice when Penelope Amari, a friend of theirs, throws herself in front of the bullet intended for Olivia.
The mounting dares turn sinister as Olivia is compelled to sleep with Lucas, but during their encounter, Lucas reveals his love for Markie, complicating their already strained relationships. Their desperation leads them to seek guidance from Inez Reyes, a former nun who provides insight into the demon named Calux that has plagued them. As Inez reveals the ritual she performed to contain Calux, the truth dawns on Olivia and her friends: they must find and re-bind the demon to survive.
Brad's dare to confront his father culminates in tragedy when he is shot by an officer during a standoff. A shocking revelation strikes Olivia as she learns that Carter and Sam are, in fact, the same person, leading her to confront the group with painful truths about Markie's family. Initially filled with anger and hurt, Markie eventually forgives Olivia, understanding the complexities of their situation.
As the horror escalates, Olivia, Markie, and Lucas discover Sam and bring him back to the desolate church to perform the binding ritual. Lucas faces a harrowing choice when dared to kill either Olivia or Markie, but his defiance results in his possession by Calux, forcing him into a deadly series of actions against Sam and ultimately himself. As Markie's turn approaches, Olivia urges her to refuse, but Calux seizes control, demanding they continue. In a desperate maneuver, Olivia engages Calux directly, forcing the demon to face the truth: the only way to elongate their survival is to involve more players in the game.
To warn others and buy time, Olivia posts a video outlining the game’s ominous rules, ending with her challenge, "truth or dare," thus ensnaring anyone who hears it into the same terrifying game, as she and Markie brace for what lies ahead.
