No, Macbeth is not always completely honest and open. The most obvious part comes in Act 3, sc. 2. In this scene, Macbeth is purposely evasive with Lady Macbeth when the two of them talk about Macbeth's nervousness. Macbeth tells his wife that he is worried when he says "O, full of scorpions is my mind, dear wife!" (l. 41). She goes on to tell him that Banquo and Fleance (who the witches have predicted will beget kings) cannot live forever. Macbeth has already talked to the murderers so the audience knows that Macbeth plans to have both Banquo and Fleance killed, but it is obvious from this conversation that Lady Macbeth does not know it. Macbeth even says, "Be innocent of the knowledge, dearest chuck, / Til thou applaud the deed," (ll. 51-52). Later, in Act 3, sc. 4, when the ghost of Banquo appears at the dinner, it is only the gulit-ridden Macbeth who sees the ghost, not Lady Macbeth. Macbeth may not have told his wife his plans because he wanted her to have plausible deniability or because he was protecting her from more crime. We aren't sure what his motive was, but it is clear that he did not share this information with her before the murder took place.