Months after the harrowing train attack that left most of its passengers dead, Amy — the last known survivor — has vanished without a trace. The incident was covered up by the authorities, dismissed as a derailment, but whispers of “something in the woods” have begun circulating among locals near the Hampshire countryside. When a new, high-speed rail line is constructed through the same forest, a group of engineers and transport officials are sent to inspect a mysterious sinkhole that appeared near the old tracks. Among them is Lewis, a troubled investigator with a past tied to the original train disaster — his sister was one of the victims.
As night falls and the team is stranded by mechanical failure, strange howls begin echoing through the forest. At first, the group believes it’s just wildlife — until one of them disappears. Panic sets in as they realize they are not alone, and worse, that whatever is stalking them isn’t just one creature but a coordinated pack. The monsters — intelligent, fast, and terrifyingly human — seem to be protecting something. Trapped between broken technology and ancient horror, the survivors must navigate not just the forest, but their own secrets. One of them, it turns out, has been communicating with the beasts — and believes the werewolves are guardians of an ancient natural order being disturbed by human intrusion.
Amy reappears halfway through the film, not as a victim but as someone changed — physically and mentally. She has lived among the werewolves, not as prey, but as a chosen emissary. She reveals that these creatures are not mindless killers but part of an old pact called the Silver Accord — guardians of balance between civilization and the wild. However, the new rail expansion has disrupted the pact, and now the creatures seek revenge not out of hunger, but as enforcers of an ancient warning. Amy offers the team a grim choice: leave and forget, or stay and be judged by the pack. Some want to fight. Others want to bargain. But time is running out, and the full moon is near.
In the explosive finale, Lewis sacrifices himself to save the others, luring the pack away with silver explosives salvaged from old mining equipment buried nearby. As dawn breaks, Amy disappears into the forest once more, her eyes now glowing faintly with the same amber light as the creatures she once feared. The survivors return to the city, sworn to silence. The government, again, covers it all up. But deep in the woods, the howling continues — not of rage, but of order being restored. And on the edge of the tree line, a new figure emerges — neither beast nor human — watching the sun rise, waiting for the next threat to the balance.
