Macbeth conceals his plot in accordance with Lady Macbeth's words: Look like the innocent flower, but be the serpent under it."
Macbeth pretends to be innocent by being friendly to everyone he is plotting against. He plays host and friend to King Duncan and Banquo and his son -- all the while plotting to have them murdered. He is the serpent under the innocent flower.
Thus, he conceals his plots by wearing the false face of friendship and loyalty.
