This episode mentions "the Stewmaker." That man was the Blacklister in The Stewmaker (No. 161) (2013). A short scene from that episode is in Reddington's flashback sequence.
(at around 19 mins) Alan Fitch (Alan Alda) exits a building and into a waiting convoy. The location is 68 Pine Street. Giveaways: the building opposite is 60 Wall Street.
Alan Alda was nominated for "Outstanding Guest Actor in a Drama Series" at the 2015 Primetime Emmy Awards, but did not win.
When Red shows up to meet Alan Fitch he says, what a long strange trip it's been, which is a line from the Grateful Dead song Truckin.