Miles Devereaux was a former member of The Alliance of Twelve. After the Alliance was destroyed, he spent years trying to reconstruct the organization.
Miles received a call from Arvin Sloane regarding a mechanism called The Index and Arvin told Miles that he was ready to start the reconstruction of The Alliance. Miles agreed with Arvin that he would meet Jack Bristow - Sloane's second in command at SD-6 - in Brussels. When they met, Miles was with two other Alliance members. He questioned Jack's loyalties because he heard rumors that Jack had defected to the CIA. Jack brushed away the concerns.
As they inserted the Decoder key with the Blackwell Index, Miles realized that it did not work; the files still remained encrypted. He suspected that Jack had indeed turned over to the government, and demanded to know where Sloane was. When Jack refused to tell him, Miles pistol-whipped him. He continued to ask but Jack refused to answer. Eventually, Miles pointed a gun to his head and asked one last time.
Just as Miles was about to execute Jack, Nadia burst through the warehouse wall, performed a 90 degree peel-out, and shot Devereaux and the other Alliance officers in the chest.