The scientific crew on the Orpheus submarine runs into severe danger in their quest to find rare micro-organisms. One crew member has died, the Orpheus has been intercepted and two of the crew are trapped and running out of air.

Cast: Molly Jones, Sinéad Cusack, James Nesbitt, Antonia Thomas, Tobias Menzies, Sacha Dhawan, Vera Graziadei, Goran Visnjic, Minnie Driver, Simon Donald, Dan Li, Nigel Whitmey, Orla Brady, Tom Wlaschiha, Nick Nevern