The sole survivor of a mysterious World War II submarine disaster is forced to fight for his life against otherworldly forces when the sunken sub inexplicably resurfaces thirty-eight years later. The year was 1943: Jack Hardy (David Jason) miraculously managed to survive an accident that would have claimed the entire crew had he perished as well. Flash forward to 1981, and that same submarine resurfaces from the grey waters of the Baltic Sea strangely intact. As the new crew prepares for deployment in the submarine, they find themselves facing a threat far more menacing than the Russians. Meanwhile, Hardy watches paralyzed in fear as the events from nearly four decades ago threaten deadly consequences for the unsuspecting crewmembers who remain completely ignorant to the horrors of the past.