Critique my time-travel plot

[kieza]

So, I'm working on a plot for a one-shot that tangentially involves time-travel, and I could use some feedback on whether it's internally consistent.

The Setup
In this setting, research into large-scale time travel is banned by the UN-equivalent, because nobody knows what will happen if it causes a paradox--universe-ending consequences may ensue. Thaumophysicists have done small-scale time-travel, such as sending back information or living creatures in situations specifically designed to create a stable loop instead of a paradox. A covert organization (a collaboration between some mad scientists and the faculty of a dwarven-secessionist university) is very interested in setting up a large-scale time machine, "in case of emergency." The idea is that, if something happens which is already screwing up the world, such as the local LHC-equivalent going awry or an invasion from the lower planes, they can use the time machine in the hopes that it won't end the world and they can fix the other problem before it happens. The machine is finished (they can't test it, though), but the project has been receiving threatening letters and parcel bombs from an unknown entity. They've hired the party to provide security for the immediate future.

The Machine
The time machine itself is mostly the generator needed to provide the massive amounts of power for temporal displacement. The actual apparatus is relatively small, mounted underneath the bulk of the generator in a small suite of rooms which can be isolated from the outside world to minimize paradox. The traveler stands in a small cubicle in the future version of the machine, vanishes, and reappears in the cubicle of the version at his destination time. The traveler can't go back before the machine was functional. The machine can safely send someone back up to six hours, and it can send them back up to four days at the cost of destroying both past and future versions of the machine. (It's single-use.) The operators have a rota of on-call travelers, so that their future versions can send someone back who have a past version present when he arrives. The past version can thus be isolated, and hopefully they can send him back again to set up a stable time loop.

The Event
Shortly after the party arrives, the "imminent arrival" warning goes off. The on-call traveler rushes into the arrival suite and locks the door according to protocol. Shortly afterwards, a bunch of explosions go off behind the door, indicating that the traveler is coming back from more than six hours up. As the explosions die down, the future version of the traveler exits the room (which is on fire) and informs the party and operators that his past self was caught in an explosion as the systems overloaded, and is dead. He explains that he has come back from three months up, after a breakthrough in temporal mechanics enabled them to make their machine more efficient while remaining backwards compatible--he's not sure, but the past machine may be reparable. Anyways, he's come back to prevent the machine itself from falling into the wrong hands: one of the dwarves working on the project passed the schematics of the project to a radical dwarven-progressivist group, which built a duplicate. Three months in the future (after the breakthrough is adapted to the duplicate machine), they send a traveler back five weeks, and using information which becomes public knowledge in that interval, they plan and execute an assassination which kills all six of the joint regents of the Dwarven Confederacy. This kicks off a world war, in which the Confederacy uses its stockpile of doomsday weapons. The traveler has come back to make sure the last aspects of the schematics don't get sent to the progressivists.

The Change
With this information, the party goes about rounding up all of the dwarves on the project. It goes well at first, but then they encounter armed resistance from some of the dwarves, confirming the traveler's suspicions. They're forced to fight room-to-room through the facility's dormitories subduing the dwarves. However, once they've gotten all of the dwarves, it turns out that the traveler doesn't know which one was the spy, and he plans to kill them all to make sure the information never gets out. Furthermore, the dwarves say that the reason they were armed is that they've been receiving anonymous letters warning them that a human government is attempting to take control of the time machine. And at the same time, one of the human technicians approaches them, saying that the information the traveler brough, purporting to explain their breakthrough, seems to be falsified--it doesn't hang together with their understanding of temporal mechanics--and that the machine should have been destroyed, but has only suffered minor damage confined to the apparatus in the arrival suite.

The Reveal
It turns out that nobody ever used the machine. The "traveler" is really just his present self, who changed clothing and applied makeup in the arrival suite after faking the arrival alert. His "corpse," burned beyond recognition, is a fake he pulled out of a bag of holding. He is, in reality, an agent for a human government which has found out about the machine and wants control of it as a weapon. However, at this point, one of the dwarves has escaped custody, and has alerted the dwarven government to the existence of the machine and the humans' attempt to gain control. The dwarves actually do go ahead and deploy one of their superweapons against the humans to prevent them from getting it, inadvertently leading to a war like the one that the agent made up. The party is forced to fight through forces teleported in by the agent, in order to regain control of the machine and send themselves back to a point before their original arrival to prevent the agent from kicking off the events leading to a global doomsday war.

Thoughts?

[Flickerdart]

How can they create a stable loop if the machine's past version is destroyed as soon as someone travels back in time?

[Shadowknight12]

It was all good until you had the PCs travel back in time.

When it comes to time travel, you have only two options, Paradox or Predestination. Either the PCs go back in time to help fulfil the very same thing they tried to prevent (Predestination), in which case everything they're doing is even worse than failure, or they actually do manage to change things up, thereby creating a Paradox and a headache for you.

The Predestination outcome is the one that makes more sense, is more logical and causes the least headaches, though it is understandably the least interesting, narratively. The Paradox outcome is the most interesting but requires that you have a plan for how to deal with it, or else your game will grind into a halt as you try to rescue your plot from a painful death.

There are several ways to solve a Paradox: Alternate Universe, Time Police, Psychic Echoes, Selective Reality Rewrite, etc. Pick the one you like best and go with it.

Or, if you want my personal opinion, don't send the PCs back in time and save yourself the hassle.

[Water_Bear]

Sounds like it could be fun. Care must be taken for several reasons though;

a) The ruse might be discovered too soon.
Make sure the body's throat is destroyed so Speak with Dead won't work, figure out why True Resurrection won't work (both in theory for the "Dead Time Traveler" and in reality for whoever actually provided the corpse), and make sure the whole apparatus is in a Secure Cavern (Mindblank on area and all occupants, Draconomicon) so that deities can't see the switch and let the cat out of the bag via Commune.

b) Time travel plays hell with plot-lines.
Just look at Primer. I still have no idea what happened in that movie, and I've spent a lot of time looking at reviews and synopsis in addition to watching it.

c) Players might not do as you expect.
Maybe they find a non-violent way to look for the "spy." Maybe they decide they want to take over the rival project and use it for themselves. Maybe they see this incident and realize time travel is too dangerous for anyone and destroy the project. Plan for contingencies.

If you're careful, this could make an epic campaign. Good luck, and remember to post a campaign journal if it works out.

[Aharon]

It was better last time :smalltongue:

[Saito Takuji]

best way to get around the paradox thing is to just make the new time period a whole brand new universe

[Roguenewb]

Any kind of predestination will make the players feel useless, and any paradox dodge (like a new universe) will make the players feel like they don't matter, because there actual home is gone. No good answer. It's a paradox, maybe I should create a new thread!

[OracleofSilence]

Several issues: as other people have said, as soon as you send the party back in time, they either cause the current events, or create a temporal paradox, removing the reason they went back, thus causing them not to go back, thus insuring that it happens... blech

Next, and more importantly: why does the party need to react violently? can they not explain to these apparently cautious dwarves what happened and attempt to logic through it? Why did the dwarves not hear the time machine "go off"? And how did this spy get access in the first place?

[Boogastreehouse]

Some thoughts:

There was a game in the 80s called Time Master, which offered a solution to time-travel paradox that allowed players to make changes to their own timeline without feeling like a pre-destined-puppet. It was a skill called Paranormal Memory.

If I recall, basically time was able to recover from most paradoxes, causing events to try and smooth things over. Extremely helpful was the fact that most time-travelers had Paranormal Memory, which allowed them to sense the events that had changed. They could thus detect a paradox and try to correct it. In the game it was assumed that a character wouldn't be recruited to be a time-traveler in the first place if they didn't possess this ability, but you could also just declare that traveling through time automatically "wakes up" this skill-like ability in a traveler, at least for a little while.

Armed with this ability, players can try to smooth time out in their own universe and to prevent a new timeline from coming into being (maybe it's theorized that too many timelines could cause the multiverse to collapse in on itself or something).

Also, depending on the players, they might be willing to be story-accomplices (because it will lead to a more satisfying story). If they know a character was found shot in the head, and they are in the past having a violent encounter with the character, they might go along with your attempts to see that the character ends up getting shot in the head.

Or they could be jerks that think it's fun to try and derail your game by, say, trying to capture the character instead. In which case, perhaps an enemy shoots the character before (or after) he divulges some information. Or the character's henchman tries to rescue the character and accidentally shoots him. Oops.

If an NPC is alive in the future, but gets killed in the past by some pesky time-traveling PCs, that's a paradox that's hard to smooth out. Try to have a few general loopholes planned ahead of time (have one of the more helpful PCs appear from even further in the future to save him, reveal the body to be that of an impostor, etc...) and drop vague hints ahead of time (maybe the PC briefly sees his future-self early on, establishing the fact that he might pop up again; maybe the players discover a hidden make-up kit and spare sets of clothes suggesting that someone is in disguise).

Time-travel is exciting because it's rarely used in RPGs. I say give it a try, but talk to your players and tell them that this is going to be a tricky game to run, and you'd appreciate their cooperation.