The evils you combat in Call of Cthulhu are by and large impersonal: alien powers (or deities) that can crush you like a bug and for whom you investigators are no more than bugs, albeit somewhat pesky ones at times.
This adventure is different. It's a tale of revenge wrought against an investigator quite deliberately, in retaliation for his past acts. As such it is suitable only for a campaign game, to be woven in amidst everything else that is going on, beginning subtly until it suddenly ramps up into an horrific climax.
The very nature of the beast means that this is more a 'scenario outline' than a full-blown adventure. The Keeper will need to fill in a lot of details based on the investigator targetted, as events need to be up close and personal - and the Keeper is the one who knows best what will work with his players and their characters. It also involves a fair bit of scene-setting, with precursor events that happen weeks or months before things really start to get nasty. Well, they do say that revenge is a dish best tasted cold!
Once the initial premise has been stated (unfortunately on a messy background that makes it a bit hard to read!), you learn of the pre-planning that needs to be done and the precursor events you need to weave into earlier adventures to make this one work effectively. Don't stint on this preparation or try to rush things, let events take their measured course in these early stages. Then things begin to heat up with a sequence of events, eventually bringing matters to a climax.
One of the neat things is that it doesn't matter what era your game is set in - 1920s, 1890s or the present day. Most of the events are timeless in that respect, or require only minor tweaks depending on the date. (If you are running Dark Ages or Invicta, you will have to put in more effort to make it work, and unlike the previously-stated eras there are no suggestions to help you.) There are even three sets of handouts appropriate to these three main eras of play, pick whichever ones are correct for your game. The standard of presentation is universally high, apart from a tendency to place 'ghosted' images behind text - looks pretty but makes it hard to read.
If this kind of very personal slow and relentless pressure sounds like it will fit in your campaign which, as I've said, needs to be a long-running one, this will prove an epic and memorable component of your campaign. Even if your players - particularly the one whose character is the target - hate you thereafter!