I've just started running Dark Heresy, and I have quite a few story ideas, but there's one that I've got in my head that really excites me, and I'd like to bounce it off of all of you to see what you think.
The rules for warp travel mention that a vessel in the Immaterium can sometimes arrive at it's destination before it leaves, which gave me an interesting idea. The players' Inquisitor receives an astropathic message from [insert hiveworld of your choice]. The message is urgent; a warp breach has occurred on the planet, millions are dead, civil order has been lost, and the government is crumbling. The Inquisitor contacts all of her acolyte squads and instructs them to rendevous at [hiveworld] in an attempt to restor order. The PC acolyte squad boards a vessel headed for [hiveworld] and makes the warp journey, only to discover that they've arrived two days before the reported warp breach. They now have 48 standard hours in which to discover the cause and put a stop to it before millions die.
Basically, it's a plot stolen from about a billion sci-fi shows.
Now comes the tricky part. If the PCs stop the warp breach, then their Inquisitor won't receive the astropathic message asking for assistance, which means that she won't send the squad to stop it (ah, time travel stories are always a headache). This would mean that the PCs will be at [hiveworld], while at the same time their past selves are in another part of the sector. There are now two sets of them. Is there any precedent in the the 40k universe for situations like these? I mean, the "arrive before you left" idea is canon, so has it ever been brought up before? How has it been handled? How do YOU think it should be handled?
Any input that you could give me would be greatly appreciated.