[she still remembers that conversation with her boss, later in her own personal timeline than his. pacing around the office, figuring out what clarence had done to turn himself into an inevitability. she offers a shrug.]

Easy answer is that my boss said I couldn't, and I trusted him more than I trusted my own sense of vengeance. More complicated one is that... man, dude, I don't know how much you know about time travel, but this bastard was jumping through time and cementing his place in the city's history wherever he landed.

[as she describes it, she at least lays to rest within her own mind any fears of clarence secretly having been teacher all along. teacher is powerful, but time travel seems even beyond him. that's one load off.]

My boss described it like a hydra. Killing Clarence in the wrong point in history would just make him sprout back up again like nothing had happened, and none of us knew what the right point was. He made himself immortal by being everywhen at once.