Lista de episodios

The submarine 'Hermes' disappears in the Arctic,along with its module 'Caspar' with marine biologist Catherine Donnelly on board. Six months later Catherine's engineer husband Clem joins the crew of another submarine,the 'Orpheus',to discover the fate of the 'Hermes',and captained by Frances Kelly,who is in an affair with married crew-man Samson. Also on board is salvage expert Raymond Hopkins,who plays Frances and Clem a recording of Catherine's last words,implying that the 'Hermes' was swallowed by something huge. The 'Hermes' is located but the 'Orpheus' gets stuck on the sea-bed with a mysterious craft hovering above it. Another crew member Maddy dies after arguing with Raymond,causing suspicion as to the real reason for his presence.

As the 'Orpheus's computer fails, Raymond protests his innocence,claiming that 'thing above' must have killed Maddy. The 'thing' turns out to be a vast Russian drilling installation,which Frances and Samson explore,discovering crewmen who died as Maddy did,leaking blood. Clem and Samson also stem nosebleeds,exonerating Raymond. The Russians capture the 'Orpheus' crew but Frances works out that the deaths were caused by the rig's nuclear reactor. Frances and Clem find evidence that the 'Caspar' was also taken on board by the drillers.

Arkady,captain of floating rig,'Volos',claims he found wreckage of the 'Caspar' in the water but Clem is not convinced. The nuclear reactor is dangerously over-heating and young crew member Vincent risks his life to shut it down,having been sworn to secrecy by Raymond,whom he saw send a message to the surface. Here the U.N. leader Lowe reveals to his assistant that he is working for Moscow and knows about the 'Volos'. Computer expert Svetlana mends the 'Orpheus' mother-board and the crew escape with Arkady and the other surviving Russian.As they pass the 'Hermes' Clem sees Catherine on board and joins her there,where she is the apparent captive of a man named Zubov.

Raymond's message is received by Lowe,giving a full account of the fate of the 'Volos' and proving he knew all about its mission. Om the 'Volos' itself Zubov tries to kill the 'Orpheus' crew, most of whom escape with Arkady,though Svetlana, the radiation-sick Vincent and Raymond are left behind and Frances,whilst feeling guilty,dares not risk her unarmed colleagues' lives to return for them. Catherine persuades her to search the sea bed for more lava worms,the eco-friendly,cheap fuel source which she had originally gathered but were destroyed by the radiation. Both Zubov and the Russian sympathiser Raymond know of the lava worms and aim to stop the 'Orpheus' mission as it runs counter to the Russian oil monopoly.Zubov tells his henchman Stas to kill Svetlana and Vincent but instead Stas hides them,pending the opportunity to escape whilst,in England,Catherine's mother Meg is aware that her house is being watched and destroys her daughter's computer and its contents.

As an American government helicopter arrives at the U.N. base Lowe gets a nasty shock. So do the 'Orpheus' crew as the 'Volos' is trailing them and is directly above them. Zubov and Raymond intend to fire a missile at the 'Orpheus' but Clem takes the capsule up into the Russian craft,thwarting their plans. There is an explosion and fatalities. On the 'Orpheus' a lack of oxygen causes the survivors to faint and hallucinate but Frances manages to overcome her situation. Can she get the 'Orpheus' to the surface and what will be the reception?