In 1973, a research team led by pregnant Constance Webb discovers an unidentified species of spider with rare healing properties in the Amazon of Peru. Ezekiel Sims, hired for security, betrays the team, stealing the spider and shooting Constance before fleeing. An indigenous tribe attempts to save Constance by having one of the spiders bite her, but she dies shortly after giving birth to her daughter, Cassandra. Thirty years later, Cassandra, now known as “Cassie,” works as a paramedic in New York City alongside her co-workers Ben Parker and O’Neil. During a dangerous call, Cassie has a near-death experience and begins to experience visions, realizing she can see into the future after failing to prevent O’Neil’s death.
Ezekiel, with limited precognition and enhanced abilities, gathers information on three teenage girls: Julia Cornwall, Anya Corazon, and Mattie Franklin, believing they are destined to kill him. Cassie, drawn to the same girls, intervenes to stop Ezekiel from ambushing them at Grand Central Terminal. She takes the girls out of the city to hide them and later finds her mother’s notes, revealing Ezekiel’s identity and powers. Despite Cassie’s instructions, the girls go to a diner where Ezekiel finds them, but Cassie manages to take them to Ben’s house in Queens for refuge.
Cassie travels to Peru to meet Santiago, the tribal chief who tried to save her mother. Santiago puts her through a ritual that separates her soul from her body, allowing her to see a plane of higher consciousness and all possible futures. She learns her mother sought the spider to cure her myasthenia gravis. Santiago tells Cassie she can unlock her true power by accepting her responsibility.
Ben’s pregnant sister-in-law Mary goes into early labor, and Ben takes her and the girls to the hospital, where they are seen on camera. Ezekiel intercepts them, but Cassie rescues the girls in an ambulance and distracts Ezekiel, allowing Ben and Mary to escape. The group lures Ezekiel to a condemned firework factory, setting traps to disorient him while Cassie calls for a medical evacuation helicopter. Ezekiel destroys the helicopter and separates the girls, taunting Cassie about her mother’s death.
Using her powers, Cassie guides the girls to safety and lures Ezekiel into a collapsing Pepsi sign, fatally crushing him. An ignited firework strikes Cassie, severely injuring her. The girls save Cassie, and she is taken to the hospital as Mary gives birth to her son. Cassie wakes up blind and paraplegic due to Ezekiel’s neurotoxin, but her clairvoyance now enables her to see fully into the future.
Despite her injuries, Cassie assures the girls that she will mentor them in their future roles. She embraces her new abilities and responsibilities, determined to guide and protect them as they navigate their destinies.