Two settings:  The far past and the near future (after Voyager)

1. Describes the early history of the Borg.  A race whose technological prowess was unrivalled in the delta quadrant.  Originally they voluntarily implanted themselves in order to fight disease and extend life.  They were benevolent and generous.  Other races in their alliance came to them and they shared willingly.

Then an alien woman approaches their elders.  She needs healing.  Once she is connected to the hive mind, she finds she has the ability to not only hear the collective, but to subvert its will.  This is the origin of the Borg Queen.

 

2. in the future timeline, the Borg are struggling with the destruction of the transwarp hub.  The Borg didn't create the hub, it was a relic from a long gone civilization.  Therefore they have to resort to slower warp technology, which has given the Alpha quadrant 25 years of peace from Borg raids.  

The alpha quadrant has remained largely at peace, and the Federation has once again turned its eyes to exploration.  Then a small ship on the far frontier near Epsilon Eridani tracks an incoming Borg cube at high warp.  It's headed straight for Earth, though it's still a good 18 months away even at that speed.  They flee and report it via subspace radio.

No signals can be detected from the cube.  The federation has to mount a defense.