Electrical – Ceiling Lighting Box HELP

There was a ceiling fan hanging and now there isn't and I need to install a plain flush mounted light.

Here's what I have: octogon box that has 4 wires coming into it, 3 of 4 wires have a black and white wire, the 4th wire has 2 sets of black and white wires.

It looks like all the grounds have been tied together. However, I tested the ground and the system is not grounded.

This is an older home. Any how. I have no idea how to wire this thing. Here's what I've figured out: one set is input power, one set of wires goes to a switch on the wall (presumably for the fixture that will be hanging), another set goes to the overhead range above the stove, I believe another set goes to the chandelier in the room because I disconnected all the wires and the chandelier no longer came on and there was some continuity there, the fifth set I have no idea what it goes to.

Here's what I did: wire nutted all the blacks together and then all the whites and kept that unknown pair wire butted together. Also connected the light fixture black and whites to the other black and whites. Turned back on the breaker. Light comes on when the switch is off, flip the switch to the on position and breaker trips.

I uninstalled the light, breaker still trips when the switch is flipped. And that's where I'm currently at. What's the 5th set of wires for?! Is that why the breaker is tripping when that one switch is flipped? The chandelier light switch works just fine and so does the stove range light. Just the one switch for that actual fixture is causing problems. I have no idea how this should be wired. Help! Please.

To Recap:
4 cables coming into box:
2 wires from switch (black and white)
2 wires from range above stove (black and white)
2 wires to ???? (black and white)
2 wires tied to other lighting circuitry in same space(black and white) SAME CABLE
2 wires power in (black and white) SAME CABLE)
Ungrounded System