Please advise about mystery plant

OK folks, you've been (surprisingly) helpful before. Here's your next assignment. It's a mystery plant that has sprung up in my front yard. It's lovely and I'll relocate it to the backyard to save it from becoming part of the dirt pit that is the front of my house this year (construction about to commence - maybe it will look nice in 6 months). But please, if you can, tell me what it is. In all my travels to the garden shops and walking around my neighborhood with the dog, I don't think I've noticed it before. The plant's shape is kind of like a stalk, with leaves coming off of it and clusters of the flowers at the top. It's about a foot tall. Click on photos to see them bigger.