Captain Frances Kelly (Driver) leads a research team below the Arctic ice aboard the cutting-edge submarine Orpheus in a quest to solve the world's burgeoning energy crisis and establish the fate of a doomed previous expedition, and expedition that took the wife of Kelly's chief engineer (Nesbitt). Enduring crushing pressure, violent volcanic gas eruptions, freezing temperatures and total darkness, the Orpheus arrives at the Lomonosov Ridge, an area of seabed within disputed territory under United Nations' administration and monitoring. Nobody ever goes there but there is something else in the freezing depths: something huge, a behemoth of epic proportions, menace and unknown purpose. As the Orpheus crew struggle for survival and attempt to unravel the mysteries of the deep, they uncover secrets more terrifying than they ever could have imagined.
James Nesbitt, Orla Brady, Goran Visnjic, Minnie Driver, Dan Li, Nigel Whitmey, Sacha Dhawan, Molly Jones, Tobias Menzies, Vera Filatova, Sinéad Cusack, Tom Wlaschiha, Nick Nevern, Richard Brake, Goran Kostic, Ron Donachie, Antonia Thomas