The Sorrowful Suitor

 refers to an unmarked quest in the Fallout 3 DLC Broken Steel.

Walkthrough
In the Presidential Metro, right before taking the train to Adams Air Force Base, go up the nearby stairs and you can find a holodisk called Sorry, My Darling next to a skeleton on a bench. The disk contains the apology of an unnamed woman to her "darling" for not being able to make it to their meeting point in La Maison Beauregard after all he had to go through to get the "special gift" for her.

Arriving at La Maison Beauregard in Georgetown, you are greeted by a hostile character called Lag-Bolt. Aside from his unique armor and shades, he also carries the key to a suitcase nearby in which you find the "special gift", the All-Nighter Nightwear.

Trivia

 * This unmarked quest is a nod to another unmarked quest in Fallout 3, Grady's Package. Grady's Package is the Naughty Nightwear and once you have found it, you are approached by Lug-Nut (who is Lag-Bolt's brother according to a note found in the latter's possession) who demands it to be handed over.

Reward

 * All-Nighter Nightwear
 * Lag-Bolt's Combat Armor
 * Lag-Bolt's Shades