Sperry portrays his work as "an indictment of subversive Muslim leaders representing Saudi Wahhabi interests … who are planting the seeds of insurrection"; its subtitle could be The Concerned Citizens Guide to Radical Islam in America. He explores how a network of Muslim groups and individuals are exploiting America's religious freedom and ethnic sensitivity in order to undermine America from within. According to the author, "The Muslim establishment plays an elaborate word game ... it is easy to be fooled by such duplicity, so I have provided readers with the intellectual tools to easily identify it." He argues that religiously sanctioned dissimulation (taqiya) enables Muslims to penetrate the U.S. political establishment to further an Islamist agenda. Anticipating accusations of anti-Muslim bias, he hastens to add that he "respects all Muslims as individuals."

Infiltration breaks down the threat to American security into seven broad categories: how Muslims conceal their Islamist agendas to gain acceptance in Washington; the hegemony of politically correct myths about radical Islam; the "silent" terror network that operates as Muslim social and religious organizations; the use of Islamic centers, charities, and mosques for terrorism; penetration of law enforcement by Muslim fifth-columnists; subversion in the military and nuclear research facilities; and corporate infiltration under the guise of religious accommodation in the work place.

Of particular note, in the chapter "The Dark Lair of CAIR," Sperry shows how groups such as the Council on American-Islamic Relations exploit catch phrases such as civil rights to push for the implementation of Shari‘a (Islamic law) in American public life and thwart law enforcement efforts to prosecute the war on terror.

Infiltration offers readers a glimpse of the "Wahhabi corridor," along Leesburg Pike that contains the "fastest growing population of Middle Eastern immigrants" in the United States and, according to Sperry, a sleeper cell community. He traced four of the hijackers to the Skyline Towers in northern Virginia (which also houses the offices funding terror) and interviewed a tenant of Pentagon area apartments popular with Saudi diplomats and Muslim immigrants who told him that, "residents ... cheered ... that very day as the Trade Center fell … The people in these buildings are animals."