By Joseph Lidster. Deep in an underground tunnel, a giant particle accelerator is about to be activated for the first time. But something strange is happening.

By Joseph Lidster.

The Torchwood team go to Geneva, where former time-traveller Martha Jones is now working as a doctor at the world's biggest physics laboratory, CERN. Deep in an underground tunnel, a giant particle accelerator is about to be activated for the first time. But something strange is happening. Scientists are hearing voices and collapsing with a strange illness. Is something lurking in the tunnel? Do the dead ever really stay dead?

Captain Jack Harkness ...... John Barrowman

Gwen Cooper ...... Eve Myles

Ianto Jones ...... Gareth David-Lloyd

Martha Jones ...... Freema Agyeman

Professor Johnson ...... Lucy Montgomery

Dr Oliver Harrington ...... Stephen Crichlow

Leon Foiret ...... Mark Meadows

Music by Murray Gold and Ben Foster.

Directed by Kate McAll.