The group are still reeling after the shocking events at the end of the last series. Now rising star Zafar joins the team as they set out to become even stronger in their battle to safeguard the nation. When London comes under terrorist attack Adam is forced to make an impossible decision, Harry must deal with blackmail threats from an old flame, and Fiona faces her own demons when she goes undercover in Syria.

• Peter Firth
• Nicola Walker
• Max Brown
• Lara Pulver
• William Hope
• Alex Lanipekun
• Geoffrey Streatfeild
• Tom Weston-Jones