Odd Wiring Configuration - Help!

I'm in the midst of replacing a lighting fixture in my dining room, and can't figure out for the life of me how this thing was wired.....all I have to work with is a black wire and a ground wire. Here's the deal:

The fixture is controlled by two switches -- one is a dimmer and one is not. There are three cables coming into the box, each with a black wire, a white wire, and a bare ground wire....there are no red wires coming in to the fixture box, but there ARE red wires connected to the switches -- I am assuming that they are somehow connected to each other behind the walls.

Here's the picture in the fixture box:

Cable 1 White is joined with Cable 2 white
Cable 1 Black is joined with Cable 2 Black
Cable 3 Black is free

and (this is the part that has me confused):

Cable 3 White is joined with the Blacks from Cable 1 and Cable 2 (there are therefore 3 wires joined together -- two blacks and one white)

The ground wires are also twisted together, although there's a loose grounding wire hanging out as well....

What gives? How do I connect this fixture with only one black wire? Could it be that something's come loose?

Any advice would be most appreciated.

Thanks

 

Sounds like a feed-through and a switch loop.
The loose black from cable three should be the hot for the fixture. THe white from the fixture should go to the two white connected together. See if this works.

gj