Snowstorms. Starving wolves. An Isolated Lighthouse. It is 1875 and Liam Robertson, keeper of the Tempest Bay Lighthouse, disappears during a series of record-breaking snowstorms on Manitoulin Island, Canada. Miles from civilization, his wife, Eliza, and their fragile, ten-year-old son are virtually trapped inside the lighthouse. When the remnants of a dog sled team drags a half-dead stranger to her door. Eliza knows she must try to save the man's life, but she soon fears that she and her son might be in danger as the man's ramblings reveal that he spent years in prison. While parceling out their dwindling food supplies, and with no way to call for help, Eliza keeps the great light burning, clinging to the hope that it will guide her husband home.