From the introduction:
Egan Bakker is a foundling from House Cannith, one of Khorvaire’s powerful Dragonmarked Houses, trying to make his way into their good graces. Bakker is an artificer on his way from Sharn to Fairhaven with his family and a suspicious collection of others. On the final day of travel, Bakker is shot and killed with a newly invented firearm.
Murder on the Eberron Express in a 3-5 hour one-shot for level 6 characters that gives you all the fun of a game of Clue, with all the variety of Dungeons & Dragons Fifth Edition. It is set in Eberron, an unusual D&D setting, that is darker and with more pulp noir aesthetics.
The 49-page PDF scenario is distributed with a ZIP archive containing numerous pre-generated characters (NPCs) and suggestions for creating additional characters (NPCs), totaling an additional 50 pages in 19 PDF documents.