Chasing the past

This is set post Hogwarts and is an alternative universe. Everyone is grown up and Sirius lives.. The battle of Hogwarts has not happened as Voldemort is still alive. Harry is missing and Sirius is near to losing his mind. Festering in The House of Black day in and day out has left him changed, but here's the thing, now is the time when everything else is about to change.