In this Time Travel Trope you travel back in time, and discover that the past isn't the way the history books record it. Worse yet, it's for no good reason. There's no raging temporal paradox, no villainous Time Traveler meddling with the time line towards his own ends. Things have just gone wrong, and it's up to you to fix history.
Probably results in a Stable Time Loop, when all is said and done.
Game and Story Use
- Once history has "gone wrong" once without provocation, what's to stop it from happening again? Does this sort of thing happen all the time?
- Could be a sign that there's really a conspiracy, or at least some wacked-out Temporal Meddler that the PCs haven't identified yet. If this has never happened in the campaign before, the PCs had better start digging for clues. Either the GM is up to something, …or the GM really screwed up.
- A genuine WayBack Trip really only makes sense if this "history went wrong" thing happens naturally, and quite frequently. As evidenced by Mr Peabody, the Voyagers, and (to a much lesser extent) Dr Who, entire campaigns could be based around this sort of recurring trouble. Great for a game where the PCs are Time Police, and every session is a Way Back Trip.
- If "time going wrong" is not a prominent feature of your setting, you'd best have a good explanation of why it happened just this once. If your rationale is weak or non-existent, the players will probably pick at it. They may think it's a mystery, and probe. If it turns out to be nothing, they may feel let down.
- The other option being that the past isn't wrong … but history is. What your PCs know about the past turns out to be radically untrue, either due to fabrication or simple incompetent transmission. Can throw a very interesting light on the status quo when they get back. Alternatively, trying to 'fix' the past may make an unholy mess in the 'present'.