Captain Jack Harkness (John Barrowman), Gwen (Eve Myles), Owen (Burn Gorman), Tosh (Naoko Mori) and Ianto (Gareth David-Lloyd) all return as the close-knit team of investigators solving alien and human crimes as they delve into the underworld of modern day Cardiff.
The high-octane storylines, filmed in and around Cardiff, include Torchwood's encounter with a rogue Time Agent; a tragic time-slip from World War One; and a memory-thief who uncovers long-forgotten secrets among the entire team
As well as Doctor Who star Freema Agyeman the series will see appearances by James Marsters who starred as Spike, the punk-goth vampire, in Buffy The Vampire Slayer and Angel and Alan Dale who is currently appearing in Ugly Betty as Bradford Meade. Dale is also well known for his roles in The O.C., Lost, The West Wing and as Jim Robinson in the Australian hit soap Neighbours.
Dale described himself as "thrilled to be working on Torchwood and delighted to be in England again. I am a huge fan of British television drama."
Marsters, who will appear in the opening episode of the series, says his character is "naughty and a bit of a psychopath."
Creator and Executive Producer Russell T Davies said: "filming is well underway in Cardiff, and we're aiming to make the show bigger and bolder than ever, as we move to our new home on BBC Two.
"It's too early to start giving things away, but we've got some amazing guest stars, fearsome new aliens, and compelling new storylines that will push the Torchwood team further than ever before."
The 13-part series is written by Chris Chibnall, Catherine Tregenna, Helen Raynor, James Moran, Joseph Lidster, Peter J Hammond, JC Wilsher and Matt Jones.