What do you mean 'back in the picture'? What are your feelings towards this ex?
Are you saying you are one of those that feel they might be tempted to rekindle that flame? If so, stay well-clear. Exes are exes for a good reason in my experience.
If you can't help yourself, book a vacation and get out of town - ignore the calls if he/she calls.
I don't know the full history here, but if you're looking for help on how to 'handle' this, then your ex sounds like bad news.
Get together with friends, they should protect you from you making a mistake with a troublesome ex.