Molly Sheridan, Carey Lowell, and Allan Sheridan entrust their newborn daughter to a new nanny, Diana Julian, unaware that the woman is actually an ancient Hamadryad bent on a terrible ritual. Diana takes the baby into a forest, approaching a giant, gnarled tree and offering the child as a human sacrifice to sustain the tree’s life. As she gazes into a pool, Diana’s reflection shifts into a growling wolf, signaling the danger lurking behind the seemingly kind exterior.
Three months pass, and Phil Sterling, [Brad Hall], and Kate Sterling, [Natalia Nogulich], have relocated from Chicago to Los Angeles so Phil can pursue a lucrative advertising career. Kate discovers she is pregnant and soon gives birth to a son, Jake, [Jack David Walker]. To balance demanding jobs, they hire a nanny; two candidates are interviewed through a nanny agency—Arlene, a young woman, and Camilla, an Englishwoman whose warmth quickly wins the household over. When Arlene dies in a bicycling accident, Camilla is swiftly hired and proves herself a steady, caring presence in the home.
One afternoon, Camilla rests in a meadow with Jake, and two things happen in quick succession. A group of three aggressive bikers belonging to an Outlaw motorcycle club attempt to assault Camilla, but she flees to the base of the living tree. The tree somehow awakens, its branches strangling and dismembering the men; wolves emerge to consume the remains, and one biker is even impaled by a root and set aflame. A few days later, Ned, the Sterlings’ neighbor who designed their house, asks Camilla on a date, but she declines. That night, Phil has a vivid nightmare in which he has sex with Camilla, a troubling dream that foreshadows the danger surrounding her.
The following day, Camilla leaves to run errands, and Ned arrives with flowers for her. Kate explains that Camilla is out, and Ned uncatches sight of her fleeing into the forest. He pursues and finds Camilla bathing in a creek, and then watches as she approaches the massive tree and appears to fuse with its bark. A pack of wolves closes in on Ned, who races back to his home and leaves a rambling message for Phil. When Camilla reappears, she is naked and ashen on the hearth, and Ned’s fate is sealed as the wolves descend on the house, leaving only a chilling reminder of the danger Camilla represents.
The next morning, Phil checks the messages: one is from a stranger, Molly Sheridan, urgently asking to speak with him, and the other is Ned’s incoherent warning. Phil visits Molly the next day; she recounts the disappearance of her infant daughter and the nanny Diana, revealing that “Camilla” is a false identity. She asks Phil to arrange a meeting with Camilla to compare her to the missing nanny. When he returns home, Phil listens to Ned’s full message and realizes it warned him not to let Camilla back in the house. Ned is missing, and Phil confronts Camilla in front of Kate, but Jake collapses with a coma-like illness during the confrontation.
Jake recovers in the hospital, but Camilla makes another attempt to kidnap him. Phil intercepts, knocking Camilla to the floor with a backhanded blow. The Sterlings flee with Jake, and they soon face a pack of wolves that trailing them toward the forest. Kate runs for the Jeep, while Phil carries Jake toward the woods, with Camilla pursuing them, levitating as she advances through the trees. They reach the giant tree, and Kate drives the Jeep into Camilla. Camilla is apparently killed, and Phil inspects what appears to be Camilla’s body, finding the faces of babies embossed in the bark of the tree.
A detective later tells the couple there is no evidence Camilla ever existed. Believing the danger isn’t over, Phil decides to cut down the tree with a chainsaw. While he’s away, Camilla—now part-tree, part-human—reenters the home. The forest-wrought threat climbs the stairs to attack Kate as Phil battles the living branches outside. As Phil hacks at a thick trunk, Camilla’s severed leg becomes a gruesome handicap in their struggle. Kate pushes Camilla out a window, and Phil fells the tree with a final, decisive cut. The tree erupts in flames, and Camilla’s body disintegrates as she falls to the ground. Bloodied but resolute, Phil returns to a shaken but safe family—Kate and Jake waiting at home—realizing that with Camilla finally dead, their home and family are now free from the threat that haunted them.
