Two days after the horrifying events in the cave, Sarah is found and washed to safety—alive, but with no memory of what happened. At the hospital, blood analysis reveals that some of it belongs to Juno, one of the girls still missing. Sheriff Vaines, suspicious and desperate for answers, insists Sarah return to the cave. Accompanied by his deputy Elen Rios and a team of specialists—Dan, Greg, and Cath—they prepare to descend once more. A new cave entrance is discovered with the help of a sniffer dog, and the group is lowered in via an old, creaking elevator operated by the mysterious Michael Reynolds.

As the team navigates the dark, narrow tunnels, Sarah suffers a sudden flashback and, gripped by panic, lashes out at Vaines, Greg, and Elen before fleeing deeper into the caves. Vaines follows, only to encounter a crawler. He fires his weapon, triggering a cave-in that separates Cath from the others. Meanwhile, Elen, Dan, and Greg stumble upon a room filled with bones—and the video camera from the previous expedition. The footage confirms the worst: the missing girls were attacked by the crawlers. Moments later, the trio is ambushed and scattered.

Elen, calling for help, attracts the creatures but is silenced by Sarah, who reminds her the crawlers hunt by sound. They watch helplessly as Dan is killed by one of the beasts. Elsewhere, Cath narrowly escapes a crawler and reunites with Greg. Together, they use their radio to create a diversion, drawing the creature away. As they delve deeper, they find Rebecca’s lifeless body hanging over a chasm. Attempting to use her remains to swing across, they are attacked—Greg falls to his death, and although Cath reaches the other side, she is killed soon after.

Sarah and Elen press on, managing to kill another crawler. During a quiet moment, Elen reveals she has a daughter, reigniting Sarah’s will to survive. Meanwhile, Vaines—lost and hunted—is saved at the last second by a battered but alive Juno, who claims to know a way out, though she’s lost her light. They soon reunite with Sarah and Elen. Despite initial tension between Sarah and Juno, the group agrees to stick together if they hope to escape.

As they near the exit, Vaines is killed in another attack. Sarah, Elen, and Juno are forced to confront a final group of crawlers. While tiptoeing past them, a badly injured Greg grabs Juno, begging for help—his cry alerts more crawlers. In the chaos that follows, the trio fights back with everything they have. Juno kills the last crawler but succumbs to her wounds. With a heavy heart, Sarah and Elen prepare to escape—only to find themselves surrounded. In a final act of sacrifice, Sarah screams, drawing the horde toward her and giving Elen a chance to flee.

Elen emerges from the cave, bloodied and exhausted, finally reaching the surface. As she’s about to call for help, she’s ambushed by Ed—Reynolds’ companion—who knocks her unconscious with a shovel and drags her back to the cave… a fresh offering for the crawlers.