Rogue N.I.D. agent, answering to the Committee, charged with masquerading as Jack O'Neill in the assassination of Senator Kinsey. Devlin gained control of the mimetic alien's mimic devices by covertly controlling several scientific analysts at Area 51 and persuading them to hand over the devices which he used to conceal himself. The purpose of this was to remove key Rogue N.I.D. troublemakers, like O'Neill and General Hammond, from the S.G.C. for the long-term goal of eventually gaining control of the command.
Devlin, realizing he was unsuccessful at murdering Kinsey, was summoned back to the Committee for further instructions. He then masqueraded as Major Paul Davis and attempted to kill Kinsey point blank, until he was caught by Samantha Carter.
Smoke and Mirrors - Devlin answers the Committee's call in the attempted assassination of Senator Kinsey, and then must go back to finish the job.