After reading the question Cloaking the USS Enterprise, I'm trying to remember an episode of TNG.
- It seems to run 3 different timelines in parallel, Current-time past time and future time.
- They all do some sort of scan at a specific spot in space, and this causes some kind of effect to happen backwards in time, threatening to prevent the formation of human life.
- Q was involved.
- There was a trial, about mankind's right to exist.
What brought it to mind was the Enterprise of the future, I think it had 3 warp nacelles... and maybe a cloak... but that's going to be a separate question once I get the episode :-)