Islamic State is here, all around us. There is no defence. Only attack. On the Syria/Iraq border, a British hostage is beheaded by IS terrorists. When the executioner breaks down, he is led into a nearby tent, where a masked figure is waiting for him. This mysterious person is treated with a mixture of respect and terror. They call him the Caliph. In Nigeria the British Ambassador and his young aide are kidnapped. A four-person SAS team is deployed to find him. The team includes Danny Black and Caitlin Wallace - an expert on West Africa. In Nigeria the team find devastation, and when they discover prisoners infected with the plague they realise they have uncovered a combined Boko Harem/IS plot to unleash a bio-terrorist attack. The team must stop the terrorists and identify the Caliph before the deadly disease is released much closer to home.