The team hatches a plan to catch the killer. Moore (Luke Evans) checks in on a friend. Kreizler (Daniel Brühl) faces his own self-doubt about the investigation. Roosevelt (Brian Geraghty) attends an event with the city’s elite. Sara (Dakota Fanning) looks into Kreizler’s past. Connor (David Wilmot) acts on impulse. 
- Dr. Kreizler: "With Pentecost tomorrow, I believe our killer will be compelled to act."
- Sara Howard (to Dr. Kreizler): "You don't have to courage to see yourself for who you really are."
- John Moore: "It may be tonight that he strikes next."
- Waltz in A Flat Major, Op. 39 No. 15 by Johannes Brahms is played at the New York Society's Gala and Silent Auction for the Prevention of Cruelty to Children.
- Fugue in G minor, BWV 578 by Johann Sebastian Bach is featured towards the end of the episode, and after the end credits.
- The episode takes its title from the Christian Feast of the Ascension, which celebrates Jesus Christ's ascent to Heaven. Traditionally celebrated on a Thursday, the fortieth day of Easter or following Sunday. Given that in 1896 Easter was celebrated April 5th, it marks the events of this episode around mid-May, 1896.
- The episode covers from Chapter Twenty-five to Chapter Twenty-six of Part II of Caleb Carr's novel, with notable changes and additional original scenes.