What could be wrong with my car?

Long story short, maybe. I have an
older car but it's in great condition.
(2000 Camry with 118k miles. Last
year we had to replace the
harmonic balancer. (The whole car
died slowly but thankfully I was
able to make it to a parking lot) Fw
to last week. Same thing happened
to my husband on the way to work
in my car. The radio shut off and
then everything else went. He
replaced the alternator and
thought it was fine. He was able to
go to and from with no problem.
Yesterday, I drove it to work and
the battery light came on.. I made
it to work and went to lunch and
the radio died. A few hours later, it
wouldn't start. The battery was
completely dead. We bought a new
battery and still wouldn't turn over
to start. A few months ago I got a
diagnostics test done and they
said my fuel was escaping
somewhere and suggested I
replace the gas cap, so I did...
anyways... im just wondering what
it could possibly be.