Weeks before he was abducted, alleged members of a kidnapping network tied to ISIS were busted in London. Syrian extremists saw it as a reason to accelerate abductions. American journalist James Foley was captured in Syria in November 2012, just weeks after the British government arrested and charged three British citizens, who were alleged members of a group of foreign fighters associated with the Islamic State, for the kidnapping of two other Western journalists. It remains unclear whether these accused terrorists who later slipped through the fingers of the British legal system were part of the same extremist cell that...