Is the Cuthbert book entitled Arrival 12:38? I believe that there are only three books that have been written on the Baltimore Plot - and of course my brain can't remember the third one.
It's called Lincoln and the Baltimore Plot, and it was published in 1949. Most of the book is based on Pinkerton's own records. It was so long ago when I read the book that I am not totally clear on this, but I think there were some differences between Pinkerton, Lamon, and Kennedy as to how things actually played out. The book also covers those differences.