Kreizler (Daniel Brühl) mourns the loss of a friend. Sara (Dakota Fanning) pushes the team to forge ahead. Moore (Luke Evans) warns his friend the killer will strike again. Cyrus (Robert Ray Wisdom) seeks revenge. 
- Sara Howard: "We have a suspect. All we have to do is find him."
- Connor: "Still trying to be a detective, are you, Miss Howard?"
Sara Howard: "Get out of my way."
- Sara Howard: "The feast of St. Barnabas is only eight days away and we know he won't stop killing!"
- Sara Howard: "We're maybe too late..."
- The title of the episode is a reference to Mary Palmer's funeral. A Requiem is a liturgical rite of the Catholic Church performed and celebrated in memory of the deceased.
- The episode covers from Chapter Thirty-Six to Chapter Forty-One of Part III of Caleb Carr's novel, with several changes and additional original scenes.
- At Mary Palmer's funeral, John Moore read the song by Christina Rossetti entitled "When I am Dead My Dearest," published in 1862.