All across the station, there have been strange appearances of orbs. They appear apparently at random, arranged in small clusters in orderly 9×9 cubic lattices. Worries increase as it becomes apparent they are some form of hive intelligence… and do not seem to be of this universe. The incursions increase in magnitude and frequency, until a ciritical point where most of the structure inside the station is occupied by orbs. It’s at this point that it’s realized the orbs have been actively working to stabilize the structure against a wave of reality warping. The orbs are the far future inhabitants of the station, come to their relative past to preserve it from a dangerous time.
There’s another story featuring an interesting twist plot. I am able to watch the episode in the order of its events, but it was originally told from the characters POV — beginning with when they wake up with no memory of how they got in their current situation. The episode as aired discusses at length the problems of taking action when no basis of understanding exists. Garak is a particular star of this one, referred to by fans as “the memory hole episode”. It’s actual title is the more obscure (hope I’m spelling this correctly) GWANTIS.