Preparing a murder mystery for player consumption

Question

At this stage in my homebrew sandbox game, the PCs are Lv14, Rogue, Cleric, Wizard and Fighter. They are also filthy rich by the usual standards of D&D, having been sailing around the world in a fast ship, working as successful merchants and doing the occasional Gentleman Adventurer thing by poking their noses into dangerous situations for the thrills. As an example of their wealth, they recently semi-casually dropped 8 million GP on outfitting themselves, their cohorts, and followers with better adventuring equipment.

So, I'm looking for ways to challenge the players with a problem that they can't solve with violence, and preferably not with magic, so I came up with the idea of a murder mystery.

The PCs, as successful merchants, have recently bought themselves a new mansion, and they've invited their wealthy contacts and other members of high society for a 'house-warming' party... but they're actually product-testing the new line of chocolates that they've been researching and developing, hoping to make sales to their home nation's elite citizens and have word-of-mouth help advertise their new product line.

So I came up with the idea of having a mystery where one of the guests is found dead. Since the house will be full of VIPs who are potential customers, the PCs obviously can't just start hitting things. All I have established so far is that the party is a catered evening ball taking place in the PC's mansion in the capitol city of their home nation. The victim is TBD, and could be one of their cohorts or allies, or any other NPC. The time of year is autumn, and the capitol is in a sub-tropical climatic zone.

However, I have a few problems in planning the event:

1. I want to ensure that the PCs have to investigate personally and not just 'leave it up to the authorities'. The players are up for the idea of a mystery session, but they are also the sort of players who want their characters to have valid hooks to get them involved.

2. I want to minimise the potential for the magic users (either the PCs or the magic-using cohorts) to simply magic up a solution. No resurrections, truth spells being of minimal usefulness, etcetera.

In essence, I want the PCs to have a reason to do their own old-fashioned investigating, and present the authorities with a solved case.

What techniques can I use to do this?

Answer 1

The authorities, really?

Do you know what pre-Renaissance (or basically anything before the mid-Victorian era) law enforcement was like? If the Sheriff can't find eyewitnesses, no one shows up carrying a bloody weapon, and no one has openly threatened to kill the victim recently, the investigation is over. The victim's family might have some suspicions, and take personal vengeance, leading to a century or so of inter-family blood feuds, but trusting the authorities to solve a mystery is:

1. A bad strategy, and
2. Kinda sad if your players are cool with someone they knew and liked having their murder "investigated" by a non-magic-using local with no real skills or expertise in solving actual crimes.

Even if they don't "know and like" the victim, having unsolved murders at your parties is a good way to get put on a social blacklist, so if they want to continue hobnobbing with the rich and famous, solving the murder is a good idea.

Dealing with resurrection has a number of options

There are quite a number of spells and magic items that prevent (or limit in a way that makes the difference immaterial to your PCs) resurrection. A weapon made of thinaun (see Complete Warrior) is a very good option here, since it doesn't require your killer to be anything but rich, no special class or spellcasting abilities needed. Bonus: If they find the killer and recover the weapon, they can resurrect the victim, giving them a stronger motivation to get involved.

Truth spells are for enemies (and the lower classes)

Your party guests are high-class rich people. These sorts of people don't appreciate having their integrity questioned, and definitely won't submit to truth spells. If your PCs don't get that social norm, and are so gauche as to forcibly interrogate one of their party guests with magic, word will get around, and these rich guests will either not interact with them at all, or only do so under the effect of divination-blocking magic.

Answer 2

1. A good way to make sure the PCs have skin in the game is to have them suspected or accused by the authorities. It shouldn't be hard as the crime happened in their mansion. Even better, what if one of them actually was, or wanted to protect, the murderer?

2. I see 2 options here:

• Have the murder committed or covered by a powerful wizard whose countermagic surpasses the PCs' skills.
• Deal with every instance of PC magic on a case by case basis. Resurrection might lead to the victim not remembering everything. Total truth spells are probably already not a thing because they would break half of all scenarios, but you could get limited pieces of truth that help investigating PCs get on the right track.

Also remember that hard-to-solve mysteries can be a source of frustration. Better to have a flexible plan and put clues in the PCs way when needed - their use of magic is one way to do that - than stick to an overly rigid solution.