PyschoSarah and Plant Planter are both right, though Sarah was a bit more encompassing in her description. For a subject use who, for any object (direct, indirect, prepositional, etc.) use whom. Who usually gets the job done. And really, isn't this just a silly nit-picky rule after all? Why can't we just hurry up with the Orwellian Newspeak already?!? #GrammarLiteratureAllusion

Since Sarah said it first she wins. Thanks for playing, kiddies!