Punish the Stars

When Hermione Granger, an Unspeakable, is given the task of researching Lord Voldemort's horcruxes, she doesn't expect to be placed in any danger. But after a potion goes wrong and Tom Riddle's soul becomes bound to her own, she finds herself quite literally haunted by the former Dark Lord. One who is hell bent on coming back to power, with or without her.