This adventure has an intriguing basis: it takes a piece of speculative fiction written in 1895 but set in 1920 and dumps the characters straight into the middle of its plot in a fine alternate history. The story is called The Repairer of Reputations by Robert W. Chambers, inventor of The King in Yellow stories about a play so warped it drove all who read or see it insane, which was adopted by Lovecraft and his followers and woven into Mythos lore.
The first part of this book is Chambers' story itself, well worth a read if you have not encountered it before and, of course, pretty-well essential if you are going to run an adventure based upon it! It tells the tale of a hideous conspiracy, one which is stopped (barely) in the story but in the adventure things are changed around a bit and it is the Investigators (naturally) that stand between a mostly-peaceful, idyllic even, alternate America and the machinations of Things That Should Not Be, a plot that would place a minion of Hastur on a newly-created imperial throne.
Next we read of the alternate history, giving America a surface tranquility but at a cost our modern minds would view as being far too high to bear. A truncated character generation system is presented to provide semi-pregenerated but personalised characters for your players who will fit in to the alternate America as it is their home. They are further developed during play, giving an almost story game air in places as once the Investigators have had a chance to introduce themselves, one is selected by the Keeper to begin the scenario and he then has to call on others as their particular talents are needed, with scope to define that Investigator's persona as they are introduced into the action.
As the adventure begins, all this is laid out clearly for the Keeper, but you will have to ensure that your players know what is expected of them. It is very much an adventure of interaction and investigation, the plot unfolding before their eyes... but violence lurks closely underneath the urbane surface, and there is ample opportunty for a brawl as the adventure reaches a climax. Various conclusions are provided, from which you can choose the most appropriate outcome based on character actions.
This is an intriguing and well-presented adventure, by its very nature a one-off, with a subtle nightmarish air to it. Pick your players carefully, with the right people it will prove a memorable game indeed.