New Town, New Home, And A New Baby?

What happens when Miss. Melody Pond, who lives with her parents, found a baby on her doorstep at their new house. Seems normal enough.....But the baby is really familiar. With his little bow-tie and sonic-screw driver. And amazing knowledge about time and space. What happened to the Doctor, how are Melody, Rory, and Amy going to fix it and how do you deal with a baby madman without his box?