heh, apparently saying 'i don't know where to even start' actually gives you some footing.
in short, flash thompson's life is spinning out of control, he violently breaks up with his girlfriend sha-shan, and all of the while he just can't find where he belongs in this life anymore. he feels like a failure and a has-been, and with good reason.
a panel from the comic.
while in this frustrated state of mind, he publicly insults the hobgoblin, and gets framed and accused for being hobgoblin himself as punishment from the enraged villain. in a few days he's broken out of prison by jack-o-lantern, which doesn't help his cause, of course. flash manages to escape jack and holes up at betty's place for a while, afraid both to get killed by the mobsters if he shows his face on the street and to turn himself in to the police, because they'll surely put him away for good and throw away the key after this stunt. nobody except flash's lawyer and his closest friends (pete, mj and betty) believe his innocence at this point. his life becomes even more miserable after hobloglin attacks him at betty's apartment, which forces him to leave in fear for betty's safety.
flash spends almost a week on the streets, he's starving, dead tired and about to give up. unbeknownst to him and the general public, the real hobgoblin is already dead, but the charges are only lifted off him after he accidentally gets involved and nearly killed in spidey's and jack-o-lantern's (who's wearing hobgoblin's costume as a trophy of sorts) fight.
more panels under the cut.