Dr. House, Medical Maverick

At the beginning of your upkeep, investigate.

Whenever you sacrifice a Clue, you may look at the top card of target opponent’s library.
You may exile that card. If you do, you may cast it this turn and you may spend mana as though it were mana of any color to cast it.

{t}, Pay 2 life: Return target face-down exiled card you don’t own to its owner’s graveyard. That player discards a card.