When The Fugitive Doctor enters the battlefield,
investigate (To investigate, create a colorless Clue token. It's an artifact with ", Sacrifice this artifact: Draw a card.").
Whenever The Fugitive Doctor attacks, you may sacrifice a
Clue (A Clue is an an artifact with ", Sacrifice this artifact: Draw a card."). When you do, target instant or sorcery card in your graveyard gains
flashback (You may cast this card from your graveyard for its flashback cost. Then exile it.) until end of turn.