Now that I've actually played this, wow... This would be worth $4 even if the gained card didn't go in your hand. Without that, it's basically an Upgrade that, instead of acting right now, acts any turn except for right now. (Ok, it would also be -1 card in that case overall, but the fact that it's non-terminal is the big deal)
Without the last line, this would be one of those rare $4 cards that actually feels good. With the last line, this is, like, Jack of All Trades kind of good.
(I should probably leave open the possibility that it shines especially brightly in the suggested Dark Ages game with Rats and reserve judgment, but... nah, this is a power card. Wait one turn for an Upgrade-into-hand? And it *can't whiff*? Too good.)
(I should probably be mad, but I'm not. I kind of like TfB cards. I can't help it. I sometimes lose games by buying too many Upgrades, but this card is actually a power card and not a n00b-trap finesse card.)