Ginger Snaps Back

Each spring, a party from a fort travels to Hudson Bay to trade pelts for winter provisions, but, in 1815, nobody returns. Brigitte and Ginger are lost with their horse in the Canadian wilderness when they come across a seemingly abandoned camp. An elderly Indian woman, who warns them that they must kill a boy to prevent one sister from killing the other, gives them each a pendant. As their startled horse runs off, Brigitte's foot is caught in a trap. Ginger seeks help, but the hunter frees Brigitte before she returns. He leads them to Fort Bailey, where they take refuge. Ginger says they are the daughters of a drowned trader and are seeking passage east.
Werewolves have besieged the fort for some time. Murphy, the fort's physician, inspects Brigitteâs wound and applies a leech, surreptitiously testing for werewolf infection. They are given a room that belonged to Wallace's son Geoffrey. Awakened by a voice, Ginger investigates the corridors, where she eventually finds the source: a deformed boy kept in a small, bolted unlit room; he bites her shoulder as he flees. When Ginger and Brigitte attempt to leave, James confronts them. While Ginger and James are fighting, werewolves attack, killing one of the residents. Reverend Gilbert leads the sisters to an allegedly safe building, which actually contains a werewolf. The sisters run up the stairs, chased by the werewolf, but the hunter appears and kills it. As Ginger and Brigitte are going to their room Ginger's nose starts to bleed; a sign that she is infected.
The sisters discover the boy who bit Ginger is Wallace's son, Geoffrey. As Ginger sleeps, he sneaks into the bedroom and wakes her. She tries to grab him, but he gets away, taking a lock of her hair; Geoffrey kills a man who investigates the noise and frames Ginger for his murder. James holds Brigitte captive as the others drag Ginger away. Wallace arrives, dismisses James, and makes a deal with Brigitte: her sister's life in exchange for their silence regarding his son. Wallace and Brigitte find Ginger at the doctor's, strapped to the examination table and held at gunpoint, about to be tested with a leech. When Wallace demands they release Ginger, Murphy ignores the order. Wallace shoots him dead, which prompts the other men to leave.
Determined to kill Geoffrey, Ginger finds Geoffrey as he cries at his mother's grave. He escapes and is captured instead by the men. Wallace arrives and kills his son himself. The sisters' protection at an end, Ginger is forced to leave, and Brigitte goes with her. Desperate for a cure, the sisters go to the hunter's cave, Ginger killing their guide shortly before they arrive. At the cave, the hunter and Indian seer woman reveal the sisters' coming had long been prophesied and that the Red and the Black would decide the destiny of the werewolf bloodline. After Brigitte enters a trance-like state, she has a vision of her destiny: the hunter attempts to kill Ginger, and she kills her sister herself. As Brigitte emerges from the trance she finds the seer is dead, killed by Ginger, who has fled. The hunter leads Brigitte back to the fort.
Back at the fort, Brigitte is taken prisoner. Gilbert tells her to beg forgiveness, but she spits in his face. Gilbert drags her out onto the parade square and prepares to burn her alive. Wallace interrupts him, runs Gilbert through with his sword, and sets him on fire. James engages Ginger in a fight, and she slashes his throat. As he falls to the ground, Ginger opens the gates and ushers in the werewolves. While the hunter holds his own against them, Wallace is soon bitten and sets the fort on fire before killing himself. The hunter urges Brigitte to kill her sister; instead, Brigitte kills the hunter and flees with her sister.
The film ends with only Ginger and Brigitte left alive huddled in the snow. When Brigitte says that she is cold, Ginger says that she is not. Brigitte then holds out her hand and presses a cut on it against a cut on Gingers hand mingling their blood and infecting Brigitte.

Question: The doctor tests Brigitte for infection by applying what to the wound?
Answer: a leech