
I know exactly what you mean. D&D groups and the like which I've played in have referred to this as Roleplay Jail, because the circumstances of the story make it either implausible, impractical, or impossible for the character to do anything which isn't related to the plot, and thus the character is effectively imprisoned by it.
Classic examples:
Hope that helps!
Classic examples:
- A cliffhanger occurs wherein the RP has to end for the day due to people's scheduling, but the actual plot hasn't wrapped up yet, and the nature of the plot is one in which the characters wouldn't have a justifiable reason to just hit the pause button and buggar off for several days.
- A "passive cliffhanger" occurs, in which there's no real cliffhanger situation, but the motivations of the characters in the plot are such that it wouldn't make rational sense for them to leave the vicinity of the plot in order to, say, go to somebody's tavern night. Even if nothing is actively occurring relating to the plot, the urgency surrounding the plot drives the characters to "remain at post".
- The plot occurs in a remote, travel-restrictive, or downright inaccessible (literally imprisoned, effectively) location, meaning that even if the plot scenes don't end on cliffhangers, it's not likely the characters could easily go elsewhere if they even wanted to.
- There are others, of course...
- Outline the plot in advance, and intentionally build in "break points" in each scheduled scene which correspond IC to the OOC need to end the scene. Usually, this comes in the form of needing to wait on something. For example, if the goal of scene 1 is to find an artifact, be flexible about exactly how it becomes found (that way you can make it spontaneous if you need to, in order to accommodate the OOC time limit on the scene). Once it's found, you declare that it'll need to be studied and researched before they can proceed, so everyone who can, please reconvene on X date at Y time at Z location (in other words, the start of your scene 2).Â
- Envelop the plot in a time pocket. This one gets trickier to pull off, and requires some preemptive discussion with participants in the plot. Let's say hypothetically you have a 4-scene plot planned out, and the only feasible point where a break could occur is between scenes 2 and 3, but OOC needs make it impractical to just do the plot as two very long scenes. Thus, you let everyone know: We're doing the RP in four scenes, dated September 1, 8, 15, and 22, each one week apart. However, scenes 1 and 2 both take place IC back-to-back on September 8, and, scenes 3 and 4 both take place IC back-to-back on September 22. Please do not use the activities which occur in the scenes we play out on September 1 and 15 in your unrelated RP, because timing-wise it won't have happened yet. If there's no good moment for a break, this can end up as a "serious time pocket", wherein you have to tell them all "okay, we're starting the scenes on September 1, but the entire plot occurs IC on September 22, so don't make use of any of it for outside RP until the plot has actually concluded".
- Reserve the plot exclusively for very active players whose schedules inherently correspond to yours. It could be useful if they're able to be active participants in continuing the RP scenario via Discord when being in-game isn't possible. This one is actually the hardest, and it's also the most limiting (due to the likelihood that your pool of participants will be small). However, it does mean you and the participants can probably stay focused and bang out the entirety of the plot in a concentrated effort, which can be an intense and enjoyable writing experience if well-executed.
Hope that helps!

Lydia Lightfoot ~ The Reliquarian's Guild «Relic» ~ Lavender Beds, Ward 12, #41
This player has a sense of humor. If the content of the post suggests otherwise, please err on the side of amusement and friendship, because that's almost certainly the intent. We're all on the same team: Team Roleplayer! Have a smile, have a chuckle, and have a slice of pie. Isn't pie great?
This player has a sense of humor. If the content of the post suggests otherwise, please err on the side of amusement and friendship, because that's almost certainly the intent. We're all on the same team: Team Roleplayer! Have a smile, have a chuckle, and have a slice of pie. Isn't pie great?