A mysterious, enciphered letter carried by a young woman of questionable morals

From 1776 by David McCulough. Page 55.

In late September, the discovery that the surgeon general of the army and head of the hospital at Cambridge, Dr. Benjamin Church, was a spy, the first American traitor, rocked everyone. Church had been one of the local dignitaries who had escorted Washington into Cambridge the day of his arrival. He was as prominent and trustworthy a man as any in the province, it was thought, a member of the Provincial Congress, poet, author, a Harvard classmate of John Hancock, and an outspoken patriot. Yet the whole time he had been secretly corresponding with the British in cipher, and was in their pay.

His treachery had been discovered quite by chance. A mysterious, enciphered letter carried by a young woman of questionable morals had wound up in the hands of a friend of Nathanael Greene, who brought the letter to Greene, who in turn carried it directly to Washington. When the woman was apprehended, she confessed she had been keeping company with Church and said the letter was his. The letter was deciphered and Church exposed. The whole army, indeed all New England and the Congress at Philadelphia, were stunned. Who could say how many other Dr. Churches there might be?

Church, who was tried, convicted, and imprisoned, kept insisting he was innocent. Sent into exile, on a ship bound for the West Indies, he disappeared at sea. Only years later did further evidence come to light proving his guilt.