In March 2016, Target USA began investigating the suspicious deaths of Russian diplomats and others around the world linked, in some way, to the Kremlin. Some of them died in the U.S. ? in New York and D.C. The deaths of some were deemed "natural." Others were obviously murdered. The investigation, which also examined failed assassination attempts, revealed a persistent pattern and a recurrent scheme involving money, power and revenge. Starting with this episode, we're bringing you a series of four podcasts examining this critical issue. We interviewed dozens of people, including victims, their family members, diplomats, journalists, U.S. intelligence, U.S. law enforcement officials and sources, members of Congress, and experts in order to gain a better understanding of how this deadly ring of killers operates.