Benedict Arnold’s treason is meticulously documented, but one of the people believed to have helped expose it is known only by a number: 355. This episode explores the mystery of Agent 355 and the Culper Ring, George Washington’s first organized intelligence network operating inside British-occupied New York.

We explain Benjamin Tallmadge’s numerical code book, in which 355 simply meant “lady,” and the invisible sympathetic stain invented by Sir James Jay. We follow the courier route from Manhattan across Long Island and the Sound, weigh the leading candidates for 355’s identity, and examine how being overlooked by British officers became a powerful weapon for female spies.

• The single Abraham Woodhull letter that is the only proof 355 existed
• Anna Strong’s black petticoat and handkerchief signaling system
• Sarah Townsend eavesdropping on John Graves Simcoe and John Andre at Raynham Hall
• Elizabeth Burgin and the escape of more than 200 officers from British prison ships
• Why historians reject the legend of 355 dying aboard the HMS Jersey