How can God have a plan, yet we still have freewill?

I'm an atheist myself, but enjoy talking about religious beliefs, so I just have a question. I was raised in Church, and I can remember asking in Sunday School why God made evil. My teacher responded that God did not make evil, but he gave man free will to follow him or not. But i also heard countless times about "God's plan for everyone." My question is how can the two exist in conjunction? If God has a plan, he planned for evil to exist, which is a pretty awful thing to knowingly put on us. If he gave man free will, how can everyone's will just happen to fit into his plan? That's not a plan, that's a guess. If he but evil on us, he can't be all good, and if he doesn't know what's going to happen, he can't be all knowing.