Using secret intelligence documents, photographs and witness testimony, the investigation reveals the secret ransoms paid for hostages in Syria and Somalia.

Secret documents, leaked from numerous intelligence agencies, offer rare insights into the interactions between spies.

A former Al Qaeda operative turned Yemeni-government informant steps out of the shadows to speak with Al Jazeera’s Investigative Unit. He reveals a sinister double game played by Al Qaeda and the former Yemeni government of Ali…