This chapter details Thomas Jefferson’s use of covert methods of communication in his engagements with Muslim Africa. In 1785, Jefferson dispatched Thomas Barclay, America’s Consul in Paris, to North Africa to secure a U.S. treaty with Morocco, the nation often known as “America’s oldest ally” in the Muslim world. Jefferson saw secrecy in Muslim lands as essential, with not only personal safety, but national security, at stake. However, little did Jefferson know that his encoded letter concerning Barclay would lead to illegible responses returned from Barclay back to Jefferson. Just one year later, it would be Jefferson who confronted an indecipherable document, staring at unreadable lines sent from North Africa—thin lines that defied his literacy, but which potentially upheld American peace.