Okay, all you better educated than me PCers. I've always had trouble with 'who' or 'whom'.

Here's the sentence I want to email today:

"You were one of four who(m) remembered."

I know 'whom' is supposed to be used generally after a preposition but, not always right? Which one is correct and, if you don't mind, could you explain to me why?

An aside: I'm contemplating on whether to leave the sentence out entirely... I want to convey the importance of their gesture, not sound pathetic like I'm having a pity party. Any thoughts are welcome. Thanks!