I find the conspiracy theories around Lincoln’s assassination pretty fascinating. There is so much we don’t know – due in large part to Stanton’s interference with evidence in the case – that many connections or ideas become plausible. I noticed a mention of John Yates Beall while perusing Wikipedia, and found this little tidbit in his biography.
There is a legend discussed by Lloyd Lewis that Lincoln was approached by John Wilkes Booth, who was a friend of Beall’s, to save his life, and that the President agreed to do so. But Lincoln changed his mind (the legend goes) when he was approached by his friend and Secretary of State William Henry Seward, who insisted that Beall’s activities had been dangerous to the citizens of New York State (Seward’s state). Supposedly a furious Booth determined to kill Lincoln and Seward for this betrayal after Beall was executed.