701.25a Only a scheme card may be set in motion, and only during an Archenemy game. Only the archenemy may set a scheme card in motion. See rule 313, “Schemes,” and rule 904, “Archenemy.”
701.25b To set a scheme in motion, move it off the top of your scheme deck if it’s on top of your scheme deck and turn it face up if it isn’t face up. That scheme is considered to have been set in motion even if neither of these actions was performed on it.
701.25c Schemes may only be set in motion one at a time. If a player is instructed to set multiple schemes in motion, that player sets a scheme in motion that many times.