The Heist

[King of Casuals]

So I'm thinking of DMing a one shot game in Pathfinder (the system doesnt really matter, just the theme) in which the players are a group of thieves who are being sent on a mission by an unknown benefactor to steal a very valuable jewel from a private collector's mansion. I'm currently thinking of letting the players approach this challenge from every conncievable angle, including having disguises, a stealthy nighttime raid, and even gathering useful info from a party that takes place the day before.

Seeing how I've never done something like this before, I thought that I should ask the playground for advice.

It should go without saying but I'll say it anyways: If you're one of my players, stop reading now because possible spoilers.

[Lord Il Palazzo]

I ran a game a year or so ago (my last 3.5 game before 5e came out) that followed a heist model. I'd planned on running it in two sessions (what I have labeled as session 1 took two sessions so the total ended up being three) but there may still be something usable for your one-shot. Feel free to ask any more specific questions you'd like about the game I ran.

Session 1: The players meet with an insider at a magically warded museum who knows that, for a few hours on one night, the wards will be down, but the museum will be crowded because of a dinner party being held there by the (mob connected) noble house that owns the place. While the players have a chance to ask questions and examine a map of the museum, they are also making plans and building their characters as a group. (The idea is that the party will be the right characters for the job, assembled Ocean's Eleven style, not just whatever adventurers the insider found at the bar that night.)

Session 2: The heist. Any pre-heist preparation (like bribing guards or casing the museum for info the insider couldn't provide) gets played out and then the heist itself happens. I have some idea what the players are planning from the discussion during session 1 so I can focus my game planning on things that are going to matter.

I left things very open ended. If you're planning for a one-shot, I would suggest planning a couple obvious angles of attack and dropping hints for your players. (Maybe there's a secret door one of them knows about or a guard known to accept bribes that could get them through the outer layer of security and gives them a definite starting point.) That way, you don't have to do quite as much thinking on your toes as you might if you left things completely open.

[King of Casuals]

Yeah, now that you mention it a two session game might be a bit more appropriate. Anything else?

[Cristo Meyers]

Just like the heist itself everything's going to come down to planning. You'll need to plan everything because there's no way of knowing just how your group is going to attack this (including, well, just attacking it). Information is going to be your players' best weapon, so you'll need to be able to give them as much as you can (that they've earned, of course).

How tough is the vault? Any spells on the vault? What about on the grounds? How many guards on rotation? How long is the rotation? Any of them susceptible to bribes (the weakest point in any security system is the person running it)?

Then the actual heist is going to revolve around what your players knew and planned for and what they didn't and is trying to screw them up. "Of course the mark knew about that secret door and put guards there. Why wouldn't he?"

You're going to want your players to be pro-actively ferreting out this info, reward them by having as much available as you can for them to find. Anything that doesn't get used just becomes fodder for the next heist they beg you to run.

[Lord Il Palazzo]

I liked the dinner party angle because it gave my PCs ways into the museum without being automatically suspicious. (A few of them burgled some random museum worker's house to steal their invitation to walk right in the front door and several others came in disguised as serving staff.) You could use a similar setup to have a party at the collector's mansion to give your players the chance to play a social angle to the heist; more people there means more eyes that could notice something suspicious, but also more opportunities to create a diversion.

Be ready with NPCs they might encounter. The mansion's owner, his family and his servants are the obvious ones but having something some others like house-guests or a business associate who's there specifically to see/appraise the gem the player's are after could throw in an interesting twist. Maybe the owner is paranoid and has hired extra guards or has mages checking for magical trickery. You don't need a full stat block unless you expect them to be involved in combat but having some clue what personalities you might have to roleplay helps a lot.

Also, don't forget that half the fun of a heist is dealing with unexpected complications or twists. Be sure your complications, well, complicate the players' plans without invalidating them entirely. Every security measure should be possible to outthink or circumvent if your players bring the right spell, ability or just creative solution. (For example, the museum in my game had alarms that would go off if a spell was cast near the exhibits, so the PCs invested in magic items with the effects of spells they wanted and longer duration spells they could cast elsewhere and carry in.) The biggest complication I threw in was that the PCs weren't the only thieves after this unwarded exhibit; another thief broke in while they were looting the place and a fight broke out (thankfully while the guards were occupied by the PCs' diversion in another part of the museum.)

[nedz]

The last AD&D campaign I ran, some years ago, featured lots of heists — though the genre was a liberation war.

I just winged many of them, but then the players often hadn't decided to do the job at the start of the session (we run very long sessions).

When I did get a chance to plan them I just made them thematic for the place they were raiding. All you need is a twist anyway — where something unexpected turns up. The security systems, magical or muscular, tend to be straightforward — assuming you know the game system.

A truly memorable heist probably needs more than one twist, most of which should be discoverable during recon.
Of course: the best twists are those which occur just when they think they have gotten away with it.:smallcool:

[Glimbur]

If you're feeling generous, you could give your PC's the ability to retroactively have done a little extra ahead of time. Call them Planning Points or something. Then, while they're in the middle of the heist, they can spend them to know various things or to have brought various items. If they need to know where the Alarm spells are on this floor, that's a couple planning points. If they need the guard over there to be a little too fond of wine, that's more planning points. And so on.

It's an extra layer of complication, but if your PCs are not great at planning ahead it could drop the difficulty curve a little. Which lets you make the heist more complicated... maybe it's not the best idea after all. But I had it and so here it is.

[Cristo Meyers]

If you're feeling generous, you could give your PC's the ability to retroactively have done a little extra ahead of time. Call them Planning Points or something. Then, while they're in the middle of the heist, they can spend them to know various things or to have brought various items. If they need to know where the Alarm spells are on this floor, that's a couple planning points. If they need the guard over there to be a little too fond of wine, that's more planning points. And so on.

It's an extra layer of complication, but if your PCs are not great at planning ahead it could drop the difficulty curve a little. Which lets you make the heist more complicated... maybe it's not the best idea after all. But I had it and so here it is.

That's a good idea. They're a bit like how Fate Points work in the FATE system. You could link up how many points they get to how much/how well they plan ahead of time to encourage them to be proactive. Plus it functions as a limited 'get out of jail free' card if your players are having trouble thinking on their feet when it all goes to pot.

[Coalhada]

Another approach is to make some skill tests be retroactive, Blades in the Dark style.
So while you might make a stealth roll in the present to sneak past a guard, you might make a perception check not to see something now but to, for example, have already observed the guards' patrol routes before you came in.