Was there an assassin on Grant's train?

[Pamela]

P. 1254 of the John Surratt trial, in closing arguments, the prosecutor described Surratt's use of a decoy to appear to be him, when he left Porterfield's house:

"He fled to the house of a man named Porterfield and there for a few days remained in concealment. Then two carriages came up, and dresses were prepared so as to have each man dressed exactly alike; and in the nighttime, when all was darkness,one man got into the carriage and drove one way, whilst the second one got into the other carriage and drove in a different direction."