And the vow, though strong, wasn’t unbreakable. Tom had fully intended to find a way around it once he’d exhausted Potter’s knowledge, but he’d changed his mind, for the time being anyway. In his past-future – Potter’s past – he’d shown some of Slytherin house he was the Heir, but kept the knowledge otherwise secret out of necessity: if it became known he was the Heir, his culpability in the girl’s death would become known, and he’d have been prosecuted.