John Wick tries to go back into retirement after getting his revenge from those who've done him wrong. It would work, except that one particular party, an Italian crime boss named Santino D'Antonio, means to cash in on a marker, a favor he did for Wick some time back, that must be repaid, pulling him in to do another job in the form of an assassination of his sister so that he can take her place in the super-secret organization. Alas, the further Wick gets in, the more enemies out to snuff him out, to the point where they are like the proverbial hydra, sprouting two new enemies for every one he takes down.