The villain has been acting like a cliche evildoer, doing dirty politics to get the hero run out of town, poisoning their lifestock, etc. This is nothing new, ever since the hero thwarted their plans the first time, they've had a long standing grudge against them. But then one day, the villain's house burns. No, the villain can't blame this one on the hero, since they were either out of town at the time, or they were arguing with the villain two seconds before. The villain has burnt roofing fall on them and can't walk away. So, they do the unthinkable, and ask for help. The Hero, unless they happen to be an Anti-Hero will probably help them. This may be the source of an instant (or eventual) Heel–Face Turn, but first a Don't You Dare Pity Me! speech. Or, it may result in nothing, because right after, the villain will take an opportunity to Back Stab.
Hello, Unknown Troper. You'll need to get known to lend a hand here.