I'm in the process of replacing a bathroom vent with light. I mean,
how hard can it be? In so doing, I have encountered some wiring
that has me puzzled as to safety and function.

What caught my attention was that I have a single, 2 wire w/ground
running to the vent. For two circuits? Hmmm. Let me see if I can
describe this.

Power to the switch box is supplied by a single two wire w/ground.
The black wire is daisy chained to both single pole switches. The
white wire is connected to ground in the switch box (???).

Now things get weird. The 2 wire w/ground running into the ceiling
has the following connections:
- the black wire is connected to the fan switch and up to the vent
fan;
- the white wire is connected to the light switch and up to the vent
light;
- the ground is tied into all the other grounds.

Up at the vent, we see the connections described as above; however,
the ground is left floating in air.
The weird part is that the vent white wires for the fan and light are
connected together (???).

I don't see the return path such that this would work. Is there
something I am missing?

Appreciate any feedback to this mess.