Was there an assassin on Grant's train?

[Eva Elisabeth]

(07-18-2015 08:07 PM)Rosieo Wrote:  This post quoted above was me putting in a good if speculative word for Mrs. Lincoln's ability to cooperate and exchange info.... I wrote it because I believe Mr. Lincoln would pick a wife with a good brain and a good heart.

And I think he did (which I have frequently stated in the past along with corrobating evidence). I don't see why Mrs. Lincoln's desire not to further investigate the assassination should be (have been!) contradictionary to this - what would it have changed or bettered about her life to know who the messenger was compared to the pain such memories caused her? The assassin was dead by that time, despite nothing would have brought her husband back to life, and Mary had partly died with him, too. Being in great, paralyzing emotional pain and depression IMO doesn't mean not to be endowed with a good brain and heart.
However, I just read on p.168 in "Lincoln's Sons" that "Robert frequently visited the box at Ford's and sat there trying to figure out how it would have been if he said yes instead of no when his father asked him to go". This was new to me, unfortunately R. P. Randall's books are not footnoted. Does anyone know where this originally comes from?