This action is the one your players will most frequently use when in exploration mode. There is no specific mechanic tied to investigating the scene: the way your players choose to explore it determines the mechanics you'll select to resolve their action.
- For PCs searching a room for clues, see the section on Perception checks.
- For PCs trying to detect a trap, see Traps & Other Perils.
When you run exploration mode, your role is primarily reactive. Much of the specifics are covered in the above two sections on Perception and traps, but here are some key takeaways to consider.
Reveal the CLues, Never the Secrets
A Perception check or other attempt to search the scene can only ever yield an indicator of the thing they're searching for, never the thing itself. If there's a hidden trap door in the room, checks will point to clues that indicate its existence (an out-of-place indentation of carpet, scuff marks from furniture, a conspicuous pedestal that throws off the room's feng shui). Player expertise activates PC expertise (the roll), which in turn yields a clue to what they're searching for.
...Except When a PC Looks in the Right Place
That being said, if a PC is right on the money when they specify where they're looking for a clue, or how they think something works, don't make them roll for it. Just let them disable the trap, or reveal the secret door outright.
Don't gatekeep the Obvious
Any clues that a PC would know due to their kit, class, or background, or notice automatically due to their abilities, are clues you should convey proactively. If the High Person encounters an emblem of one of their houses plastered on a wall in a dungeon, that PC would already know what it means, so it's a pointless exercise to gatekeep that information behind a roll.
Don't Let Everyone Roll For IT
A failed attempt to search for clues will not yield new clues if the strategy or subject of the search doesn't change. If multiple players want to search, don't let them all roll, as that skews the probabilities wildly in their favor: instead, appoint the most "investigative" among them (in accordance with the rules of group action) to lead the search, and let the others help; until the nature of the search changes, the outcome stands.
On Passive Perception
Other games may have mechanics that give you a metric by which to measure if a PC automatically notices something without their having to roll. This is often called "passive perception."
The Purpose of Passive Perception
The passive perception mechanic is meant to solve a number of problems, like reducing the amount of rolling the table has to do and preserving the player's immersion when a PC fails to perceive something happening outside his awareness in the scene. That is, if a player has to roll to determine if his PC notices something and he fails at that roll, then the player is made aware that there is something in the scene that went unnoticed, even though the PC is unaware.
Even so, OSR+ does not use passive perception. One problem with passive perception is that it requires you to behave like a video game engine, remaining constantly vigilant of each player's passive perception score to make sure the players don't miss anything their PCs wouldn't. This may not seem like too much of a burden for four players in a vacuum, but such vigilance detracts from your focus on the fiction and requires you to be active rather than reactive in exploration mode, when the players should be the ones driving the action.
Making Due Without Passive Perception
So, if we don't have a number to silently check against when we're uncertain if a player might notice a trap or a hidden door, what do we do?
- First of all, there shouldn't be anything in a scene that if left undiscovered by the PCs gatekeeps an adventure hook in such a way that the adventure can't continue. That's not a failing of the mechanics, that's a flaw in the design of your adventure.
- Second, we already establish in the rules of Perception that players are only ever entitled to skill checks when they have their PC do something in the fiction. While you don't want to make players roll for things their characters would reasonably know (e.g., a Ranger or a PC with the Survival skill will most likely know how a bear trap operates), you don't have to proactively inform your players about hidden things in the scene unless they interrogate it. Therefore, if they're wandering through enemy territory in the woods and nobody thinks to check for traps, they may just walk right into that bear trap.
- Finally, the PCs' ignorance of the players' awareness of some danger is not as big of an issue in OSR+ as it is in other games, where player skill trumps character skill. Players are encouraged in this system to play to their heroes' competence, not their own. Moreover, it's not a bad thing to create a sense of suspense for the players, even if that suspense derives from out-of-character knowledge. For example, if the players know their PCs are being stalked by something in an abandoned spaceship, that's fun for the players, and creates a challenge for them to roleplay toward their PCs' ignorance.
When it comes to knowing when to call for a Perception check from the players, look to the fiction for guidance. If you have a stealthed NPC that plans to ambush the players, the PCs don't get a Perception check to avoid the surprise round unless they already suspect they're being stalked or they already happen to be on the alert for some other reason. It's the same situation as setting up for an attack of opportunity: unless the players have positioned the fiction such that the attacker has their opponent cornered, there's no opportunity to make an attack when the opponent disengages from them.
The Truth is Subjective
Anything you reveal from the PCs' perspective (outside of special abilities that yield an objective truth, like the spell True Sight) can only yield insights from their perspective.
For example, if the PCs have searched the room and turned up nothing (even if the check involved was successful), you should always narrate their finding from their perspective: "it seems the thing you are searching for is not in the room" rather than "the room is empty." This is especially important when PCs fail the same check. Consistency is key: if the PCs become accustomed to your responses as being the same whether their roll yields success or failure, they will have to decide for themselves what to do next rather than trying to read your poker face.
No Check is Meaningless
Sometimes you might accidentally mislead the players by overstating the importance of something in the scene, e.g., implying the scene contains a discovery you didn't plan for. You will find them rabidly investigating the scene in hopes of turning over this non-existent discovery. There are a number of ways to handle this situation:
- On the one hand, you can let them make an attribute check with a binary result, and definitively reveal that after an exhaustive search, the PCs believe they've found nothing. This route shuts things down completely, but it also shuts down the momentum of the investigation and can lead to disappointment, especially if the players put a lot into the search.
- You can ask the dice. If you call for a success check, it's possible the dice will yield GM advantage or player advantage: in the former case, you could create a discovery that in turn acts as a clue to the discoveries you actually planned for in the scene; in the latter case, you could invite the players to add to the scene to the same effect.
- Finally, you can borrow an adventure hook from a floating scene (or even an adventure hook from elsewhere in this scene) and surface it here.
Whichever option you choose, you want to meet the players' investment in the scene with an equal enthusiasm on your part, even if that means playing Schrodinger's cat with your adventure hooks.