Doc Aurlock, Grizzled Genius

Plot abilities are written “Plot [cost],” which means “Any time you have priority during your main phase while the stack is empty, you may pay [cost] and exile this card from your hand. It becomes plotted.”

You can’t cast a plotted card on the same turn it became plotted. On any future turn, you may cast that card from exile without paying its mana cost during your main phase while the stack is empty.

Exiling a card using its plot ability is a special action. Once you announce you’re taking that action, no other player can respond by trying to remove that card from your hand.