You have learnt the story of Regulus, who died heroically, drowning in the lake infested with inferi. His fate has moved you deeply and you feel inwardly it was unfair that this young man had to die so young. You manage to get your hands on an improved self-invented time turner that can take you to his times permanently. You know it will change your life completely but you're ready to make that sacrifice. You go to the cave where the horcrux used to be hidden and you go back in time to the moment when Regulus was there. You arrive just in time to see him replacing the horcrux locket with a fake one.