Lydia Darragh's house happened to be across the street from General William Howe's headquarters, and the night of December 2, 1777 British officers commandeered one of her rooms for a secret conference.
[4] Darragh began regularly providing her son Charles with information regarding the enemy's plans, gathered by eavesdropping in her home and around town.
She would often write this information in simple code on pieces of scrap paper, which she hid in large buttons that she and the messengers wore.
Prior to her meeting Howe, a British officer introduced himself as Captain William Barrington of the 7th Regiment of Foot (Royal Fusiliers).
They were permitted to remain, as Quakers were known to be unsupportive of the war, even on the side of the colonies, and therefore posed no apparent risk to the British army.
She learned that British troops were being ordered to leave the city on December 4 to make a surprise attack on the Continental Army camped at White Marsh, led by George Washington.
Lydia sneaked back to bed and pretended to be asleep until the officer, Major John André, knocked three times at her door to awaken her to follow them out and extinguish the candles.
Along the way she met an American officer, Colonel Craig of the Light Horse, and told him about the impending British attack so that he might warn Washington.
After the British troops attempted their attack and realized that the Americans were waiting for them, fully armed and expecting the assault, the officer questioned Lydia and asked if anyone was awake on the night of the meeting, because it was obvious that someone had betrayed them.
A quote from the officer who questioned Lydia: "We were betrayed, for, on arriving near the encampment of General Washington, we found his cannon mounted, his troops under arms and so prepared at every point to receive us that we were compelled to march back, without injuring our enemy, like a parcel of fools.
— After Dinner a little poor looking insignificant Old Woman came in & solicited leave to go into the Country to buy some flour — While we were asking some Questions, she walked up to me and put into my hands a dirty old needle book, with various small pockets in it.
surprised at this, I told her to return, she should have an answer — On Opening the needlebook, I could not find any thing till I got to the last Pocket, Where I found a piece of Paper rolled up into the form of a Pipe Shank.
On December 6, 1777, after the British returned from Whitemarsh, a message was published in the Philadelphia newspaper about "a poor woman, whom we both know" traveling to the Frankford Mill: The following letter was found in a bag of Indian meal, which was picked up on Saturday the fourteenth of last month, was supposed to have been dropped by some of the women who were coming into town, when the skirmish happened between the pickets.