Nine graduating students travel to a remote island to shoot a short film for their final school project. The group includes timid Eunice Janella Salvador; her best friend Olivia Jane Oineza; Olivia’s boyfriend Kenly Diego Loyzaga; Kenly’s best friend Justin Yves Flores; party-girl Richalaine Maris Racal; classy Marie Sofia Andres; jokester Gerard Empoy Marquez; shy photographer Kiko Elmo Magalona, who admires Eunice; and newcomer John Ronnie Alonte. They stay at Olivia’s parents’ summer home, where they meet Mang Pedring, the eerie caretaker.
Tensions rise when Olivia discovers Kenly has been cheating on her with Marie; Eunice knew but stayed silent. After a heated confrontation, Olivia forgives the group the next day, and they begin filming. A storm interrupts the shoot, and that night, they play a game called Bloody Crayons, a twisted version of truth or dare involving a box of colored crayons, each representing a challenge or consequence. Red crayons involve mixing a drink the last drawer must consume.
As the game escalates, Olivia draws a blue crayon and reveals she slept with Kenly, reigniting conflict. Marie draws the final red crayon and drinks the mixture, but she suddenly vomits blood and dies. Panic spreads. Olivia runs, and Kenly chases her. Olivia falls off a cliff to her apparent death, and suspicion turns on Kenly. Kiko and John tie him up. Later, they find Kenly murdered, his throat slit. Justin grabs a gun, accusing others. A fight breaks out, and Gerard is accidentally shot. Richalaine grabs the gun and flees upstairs. Justin corners her but slips and knocks himself out. Eunice finds her friends as John disappears into the woods.
Gerard dies from his wound. Richalaine and Eunice are later chased by someone in costume. They escape but Justin, now deranged, attacks them with a knife. In the struggle, he and Richalaine fall down the stairs and die. Eunice and Kiko reunite and encounter John, who claims to have found a boat. Kiko becomes suspicious after learning John has Mang Pedring’s keys. John says the caretaker died in a trap. They fight, and John falls into a pit but survives and discovers it leads to the cliff where Olivia fell; yet her body is gone.
Reaching the shore, the trio finds a boat, but Olivia’s voice comes over Eunice’s walkie-talkie. They return to the house and find her alive. Kiko grows suspicious; Olivia appears unharmed. He tries to warn Eunice but is stabbed by Olivia, revealing she orchestrated the deaths. Olivia hunts Eunice through the woods, ultimately cornering her at the cliff. Olivia confesses she planned to kill only Kenly, Marie, and herself but claims the others' deaths were not her fault. The two fight. Just as Olivia is about to kill Eunice, John’s drone crashes into her, knocking her off balance. Eunice tries to save her, but Olivia lets go and falls to her death.
John, alive thanks to a bullet-stopping dog tag, helps Eunice. They hear Kiko’s weak voice on the walkie-talkie and escape the island together by boat.
