The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 8: Soldier Life and Secret Service.
Francis Trevelyan Miller, Ed.

Sheridan had the born soldier's contempt for such characters, and though setting the man to work, as suggested, he had him watched by soldier scouts who had been organized under Colonel Young of Rhode Island, and when later there was brought to him at midnight, in complete disguise, a young Southerner, dark, slender, handsome, soft-voiced, and fascinating in manner—a man who ‘had had a tiff with Mosby,’ they said, and now wished to be of service to the Union and act in concert with Stanton's earlier emissary, ‘Mr. Lomas of Maryland,’ Sheridan's suspicions were redoubled. The newcomer gave the name of Renfrew—that under which the Prince of Wales (Baron Renfrew) had visited the States in the summer of 1860—and was an artist in the matter of make — up and disguise. Sheridan kept his own counsel, had the pair ‘shadowed,’ and speedily found they were sending far more information to the foe than they were bringing to him. They were arrested and ordered to Fort Warren, but in most mysterious fashion they escaped at Baltimore. A few weeks later and Stanton found reason to believe that his friend Lomas was closely allied with the conspirators later hanged for the assassination of Abraham Lincoln, and then it dawned upon Sheridan that Renfrew was probably none other than John Wilkes Booth.

At best, therefore, the information derived from such sources could never be relied upon, at least by Union generals, and Sheridan's scout system was probably the most successful of all those essayed during the war. It was also most daring and hazardous, for the men took their lives in their hands, and the chance of immediate and ignominious death when they donned, as they had to, the Confederate uniform and penetrated the Confederate lines. There, if suspected and arrested, their fate was sealed. Yet it was one of these who successfully bore to General Grant, Sheridan's urgent ‘I wish you were here,’ when, on the 5th of April, 1865, the latter saw slipping away the chance of penning Lee's harassed and panting army