Held captive on a new high-tech rig, the Bravo crew are launched into a rescue mission deep beneath the sea. But Pictor have not revealed all they know about what lurks on the ocean floor...

Fulmer's rift with Rose leaves him open to manipulation from Coake, but his plans to exploit Fulmer are interrupted when Cameron takes a drastic step.

Laden with explosives, Magnus, Fulmer and Bremner head onto the Arctic glacier to bring aid to those trapped below.

Trapped in the Subsea Module, Rose and Cameron must stop Pictor getting the data drive. But an ambush on the Wet Dock leads to a gunshot that changes everything.

The Bravo team race against time to reach the Heart of the Ancestor before Pictor. But when they learn that Darian still has an ace to play, Rose and Fulmer have no choice but to give themselves over to a heroic act of self-sacrifice.

After a shocking death on board, the team are tested to their limits by a deadly blizzard that brings them into close contact with the Ancestor – and another danger even closer to home.