The Orpheus crew have found rare bio fuels in the ocean depths, but they must find a way of getting it to the surface safely. With the Russian captain of the Volos submarine determined to stop them, will they manage to stabilise the energy source and make it back to the surface?

Cast: Dan Li, Nigel Whitmey, Ron Donachie, Richard Brake, Minnie Driver, Orla Brady, Goran Visnjic, Tom Wlaschiha, Tobias Menzies, Goran Kostic, Sacha Dhawan, Vera Graziadei, Nick Nevern, Molly Jones, Sinéad Cusack