Examining how the so-called Islamic State's terror network has been operating secretly in Europe, and Western intelligence agencies' battle to stop it, from highly organised cells, like the one that killed 130 people in Paris, to lone attackers within communities.

Sara Green was a teenager betrayed by a mental health system designed to protect her. Using Sara's own words taken from her diary, Panorama reveals the failings of a Priory hospital where she was an inpatient and where she took her own life in a misjudged cry for help. Peter Marshall asks what lessons can be drawn from Sara's story and what can be done to fix the country's broken child and adolescent mental health system.