The young Mulligan grew up at a time when agitation over Britain's taxation of the American colonies was rising; born in Ireland, he moved to the colonies at the age of six, and considered himself not merely a colonist, but a patriot of the impending nation. Able with dialogue and persuasion, it was Mulligan who convinced the young Alexander Hamilton to join the patriotic movement for independence.

During the War of Independence, Mulligan continued to work as a tailor in New York. Such work was ideal for knowledge gathering; many of the British officers would attend his shop, and from the dates they wished to collect their new or updated uniforms, Mulligan was able to pass along information about the deployment of certain regiments. A fortunate visit late one night by a British officer demanding service yielded vital knowledge of a daring plot to ambush and capture George Washington: by informing the revolutionary leader ahead of time, General Washington's capture was averted.

Mulligan is often termed an 'unsung hero', as his deeds - crucial to the war effort - have faded from memory over time. This biography not only tells of Mulligan's importance, but includes in the appendix the man's own written narrative upon his deeds.