When the Kinloch Bravo's crew find themselves stranded on their production platform, first when their chopper is diverted and then by a mysterious fog that affects the entire oil field, rig boss Magnus' attempts to find a practical solution are thwarted by a horrifying accident and a growing sense of unease onboard.

With Baz missing and presumed dangerous, the crew split into groups to search the production module and find him, and Rose takes the painful decision to isolate Fulmer. But as Rose makes a perplexing breakthrough, the manhunt becomes more frightening and mysterious when the crew are hit by power failures and paranoia, and they discover things that push them far beyond their comfort zone.