Amy and Rory are gone now, and there is a hole in the Doctor that he has contended with so many times before. It's bigger than ever though, and even he has no hope that it can be filled. Stranded in Ponyville at the height of his depression, only Ditzy "Derpy Hooves" Doo has a chance of returning the Doctor to his old self. The problem is that when dealing with a broken Timelord, two hearts need fixing instead of one.