The Creep

Always have a backup plan, my friends. Whenever I set out to stop the annihilation of the human race (a painfully recurring task, I might add), I leave myself one ‘redo’ in case I fail.
Tomorrow I will fail.
I’ve received a message from my future-self with a warning of what to do differently next time. Usually that is enough for me to course-correct and prevent catastrophe.
This time the message said ‘Send Someone Else’.
You there! You reading this! You ARE Someone Else! You’re exactly what I’ve been looking for.
This threat is terrifying, my friends. Quite unstoppable, once it reaches a certain mass. Only chance is to cut it off at the bud. I’ll send you to the initial outbreak point, a chemical factory with just what we need to kill this thing before it consumes all.
Yours is a mission of herbicide.