You want to remove the hallway and isolate the dancing man. Rotoscoping frame by frame may be your only option, normally when you want to isolate a figure from the background you shoot to footage on a blue or green screen and then use a chroma key to remove the background.
There is no simple method if the footage wasn't shot with that intention. No software (except on CSI) has that ability.
I haven't used it, but AE comes with one of Imagineer Systems Products. It's called Mocha or maybe Mokey?
Imagineer makes tools for creating travelling mattes for objects shot against generic backgrounds. "Mattes are created using the background information and the motion data, allowing you to easily create mattes for objects shot against virtually any background."