Neither Mr. Awlaki nor his prospective wife knew it, but their match was being managed by a Danish double agent as part of an attempt to help the Danish intelligence service and the C.I.A. find the cleric’s hiding place in Yemen. The attempt failed, but the undercover agent, Morten Storm, 36, a former motorcycle gang member who had converted to Islam, continued to communicate with Mr. Awlaki. When Mr. Awlaki was killed in a drone strike on Sept. 30, 2011, Mr. Storm was certain his efforts had been instrumental in it.