Will Stanton, portrayed by Alexander Ludwig, is on the cusp of his fourteenth birthday, a pivotal moment that invites both anticipation and impending peril. As Will and his siblings stroll home, they encounter the enigmatic Miss Greythorne, played by Frances Conroy, and her loyal butler, Ian McShane, who extend an invitation to a lavish Christmas party. Shortly thereafter, two unfamiliar farmers, Dawson (James Cosmo) and Old George (Jim Piddock), arrive at their home carrying a sumptuous Christmas tree ordered by the Stanton family. Despite the joyous spirit, these farmers eerily know Will’s name, offering him birthday wishes while ominously predicting foul weather on the horizon, even though the skies are clear.
Living in a new English village after relocating from the United States, Will feels overshadowed by the festivity of Christmas, which often eclipses his birthday. The only acknowledgment of his special day comes from his younger sister, Gwen (Emma Lockhart), who presents him with a thoughtful gift—a rugged Casio G-Shock Mudman wristwatch. Will's world shifts more dramatically when he finds his living space usurped by an older brother returning for the holidays, forcing Will to retreat to the attic—a clear metaphor for his burgeoning feelings of isolation.
As a gift, Will decides to purchase an intriguing stone pendant for Gwen at the local mall. However, his innocent act of kindness quickly turns sour when two dubious security guards accuse him of stealing. In a disconcerting twist, the guards morph into aggressive rooks under the harsh flickering lights, prompting Will to tap into mysterious powers he never knew he possessed in a desperate bid to flee their grasp.
Will's strange experiences do not end there; presented with a distinctive Celtic belt from his oldest brother Stephen (Jordan J. Dale), he finds himself at the Manor Christmas party, where unsettling encounters await him. Here, he encounters Dawson and Old George once again, who seem to possess secrets about his destiny. As Will grapples with his feelings for Maggie Barnes (Amelia Warner), a captivating local girl, his turmoil escalates further when an ominous figure on a white horse, known as The Rider, threatens his life. Thankfully, the Old Ones—Miss Greythorne, Merriman, Dawson, and Old George—arrive just in time to save him.
The Rider, a menacing entity, warns them that the power of The Dark will rise in five days. As Will learns, he is the last of the Old Ones, the fabled “seeker” destined to uncover six powerful Signs that will enable The Light to combat The Dark's growing strength. Though he is reluctant, believing himself to be merely the sixth son rather than the seventh, the stakes are high, and his lineage carries a tremendous burden as the clock ticks down.
Returning home with newfound knowledge, Will discovers that his life harbors many more twists. He faces the shocking revelation that he had a twin brother named Tom who vanished mysteriously during infancy. Training under Merriman's guidance, Will learns to harness extraordinary powers: from commanding light and fire to slipping through time and deciphering the Book of Gramarye's ancient text.
Throughout his journey, Will encounters various challenges, including a manipulation from The Rider that involves his older brother Max. As days slip by and storms brew outside, the dark forces become increasingly aggressive, culminating in a harrowing blizzard that threatens the village. The chase for the six Signs intensifies when it's revealed that Maggie, who initially captivated Will's affections, is embroiled in the conflict, ultimately revealing her allegiance to The Rider in a bid for eternal youth. Betrayal unfolds rapidly, leading to her tragic demise.
As The Rider's relentless pursuit continues, mediating between realms of darkness and light, Will and the last of the Old Ones take refuge within the Great Hall, knowing that the Rider can only enter with permission. However, his cunning manipulations manage to circumvent these barriers, as he impersonates the familiar voices of Will's family, gaining access at a critical juncture.
Now trapped in a sinister cloud where time bends and the shadows loom, Will deciphers the final enigmatic riddle: he himself is the sixth Sign. With this revelation, he wields newfound strength, rendering The Rider powerless as Will identifies and secures all six Signs. Ultimately, he manages to entrap The Rider in one of his own glass spheres and disperse the encroaching darkness, returning balance to his world. In a heartfelt reunion, Will finds solace as he embraces Tom, reuniting with his long-lost sibling while returning to the safety and warmth of his family.
