One of my biggest failings as an early GM was a sort of fear to deviate from published material. If it was on the page, that was what happened, come hell or high water. Oh, sure, I read the occasional advice column that talked about tailoring the adventure to your PCs, but it was always couched in terms of matching the adventure to their capabilities. I never had a good example to go by for really integrating a published module into a campaign. Fortunately, I was able to learn by trial and error, but I thought I'd try and put down some of the process here in the hopes that it can help someone's campaign out of where I was stuck for many years - or open up other GMs to the idea of using published adventures.
Our subject this time around is the venerable Basic D&D adventure "Castle Caldwell" (originally part of B9 Castle Caldwell and Beyond - I'm using B1-9 In Search of Adventure). I actually forgot how bad it was before I trailed the hook in front of my players and they nibbled, but that will make it a great example. Since my players have largely cleared out the castle, I can now reveal some of what I was doing behind the scenes.
The adventure itself has the thinnest of plots (you are hired by a merchant to clear monsters out of the castle he recently bought), a terrible map (more on this later), and what appears to be a completely random selection of low-level monsters sharing rooms in the castle with no rhyme nor reason to their presence. Human traders live just down the hall from goblins while a small bandit gang and their mule camp in another room. I felt like it was my job to both make some sense out of this as a GM, and make it interesting to the players as more than just another dungeon crawl.
I. Baiting Your Hook
The first, simplest, and easiest technique for tying any given published adventure into your campaign is one that I didn't actually use, and that is to tie the "hook" for the adventure directly to the PCs. Instead of a random merchant seeking adventurers in the local rathskeller, Caldwell could be someone with links to the party: a previously known NPC who they owe a favor to, a powerful merchant they need to get on their side for some reason, or even a relative of one of the PCs. If you're willing to take a chance, you could even eliminate Caldwell entirely and have one of the PCs inherit the monster-filled castle.
This sort of technique works best when the game has been going on for a while and the players have developed strong relationships with the NPCs involved. It could also be used for players that have a strong engagement with their character's background. Some players don't like to focus too much on their PCs background - especially if they prefer to develop it in play. For those kinds of players you'll need to take a different tack and bait the hook with something of interest to the player.
I chose not to use this technique this time around mostly because this turned out to be the first adventure of the campaign, and I wanted to emphasize the wide-open nature of their choices - Caldwell's offer was only one of several rumors the party heard and could have followed up on. I think if there had been a close tie to one or more PCs built into the hook, it would have made the other possibilities seem like alternatives simply put there for the illusion of choice.
II. Seek Explanations Outside the Module
One of the big things that makes a published adventure feel like it has been just dropped in the center of a campaign is the lack of connection to the rest of the world. Ideally, players should not be able to tell when they are in a published module vs. a situation or adventure that you have designed, and the key to that is smoothing over the transition areas so they can blend smoothly with the rest of your game world.
You can use this technique to take care of another problem with published adventures at the same time: sometimes, the adventures just don't make sense. When I read through Castle Caldwell I found myself asking a lot of questions. Why are all these creatures in the castle? Why aren't the brigands robbing the traders? Why are both groups OK with the goblins that are wandering the central corridor? Are these monsters supposed to be unaware of each other?
My first chance to blur the edges actually came on the way to the adventure, when a random encounter turned up a trio of bandits. I decided these ne'er-do-wells were connected to the bandits inside the castle and (since one of them had an extremely low hp roll) that they had recently fled from a previous encounter. The party made short work of them and went on their way, thinking nothing of it. When they made a cold camp outside the castle and set to observing it, I saw my second chance - I had the traders arrive at that point, and gave them the mule (originally supposed to belong to the bandits.)
Slowly I started filling in the connections from there: the traders were renegades from the Duke's army, and they were supplying the goblins (and bandits) with weapons and armor. Now I had an explanation for the presence of the three major intelligent groups in the castle, which I can tie back to one of the rumors at the start that the PCs didn't pursue.
The key for making this kind of connection is to ask yourself "what do I know that could explain this?" before you ask "how can I change this to make sense?"
III. Don't be Afraid to Change
You won't come up with an explanation for everything, and that's OK. Sometimes it's not worth it - take the aforementioned map, for instance, which you can see over on the right. There's no way to make that layout exciting or believable. Besides the castle only having a single floor (you could conceivably work with that - maybe it was ruined, or abandoned partway through construction) you've basically got one long hallway with doors off of either side of it. Players aren't getting in unless they go through the front door, and after that it's one long slog of "open the door on the left, OK, now open the one on the right."
Someone else had the same problems with the castle that I did, and he'd already done the hard work of remapping the place to make it both more logical and more interesting.
You can see his efforts over on the left: it's easy to see how the layout is a lot more interesting, especially with the postern gate in the kitchen and multilevel rooms he's introduced (the main hall and dining hall). My players used the back door almost exclusively, and fought a major combat starting in the front hall, ranging up the stairs to the balcony, and across the dining hall as their outclassed goblin adversaries tried to reach and warn their human allies. It was roughly eleven thousand times more exciting than a door-by-door slog.
Changing things is fine, but I try not to make it my first resort - often you can come up with an explanation with a little thought, and that explanation is likely to lead to a plot thread that your players can explore (letting you tie it into some other adventure!)
I've still got some more techniques in my bag of tricks, but they're going to have to wait for Part II of this essay, where we'll resume with:
IV. Make Your Own Serendipity
(to be continued…)