a couple of months ago we added a foundly kitten to our household which
already had a ~2 year old neutered male.  the older cat did not take to
the new arrival exceedingly well, there were rough&tumbles and hissing
and the like, but up until a couple of days ago things seemed to be
going OK.  they hung out together, chased each other around, ate out
of the same bowl.

the kitten seems to be doing great.  he's grown a lot, he's full of
energy.  the older cat is eating a lot more though, and he's put on a
_lot_ of weight.  he scratches a lot and licks and cleans himself much
more than he used to, but we figured it was fleas or something and that
a flea-treatment would deal with it.

a couple of days ago the older cat began exhibiting strange behaviour.
he started hiding in really odd places (for him), such as under the
kitchen sink or on my bedside table.  all the time.  i mean _all_ the
time.  pick him up (oof! he's heavy), he complains, put him down, and
he's right back in/up there again.   he won't come down to the floor.
he seems to be wary of the kitten, hisses at him if he comes near.

we examined him and found an irregularly-shaped bald patch about
0.5 x 1.0 inch on his back.  it looks like a chunk of hair either
fell out or was ripped out.  touching it doesn't seem to hurt, and
he appears undamaged aside from that.

if the kitten isn't around, he's pretty relaxed and sleeps a lot.
but the moment the kitten shows up, he seems to get agitated.

the kitten seems pretty confused about this.  he wants to play with
the older cat, but the older one wants nothing to do with him at all.

has anybody encountered this kind of situation before?  if so, what
did you do?  how did it resolve?