Act 2 Macbeth journal entry

In the second Act of Macbeth it goes to inform us about how Macbeth commited a murder on the king using a nights dagger leaving it bloody ,and with Lady Macbeth being appalled by the actions.In this act, i feel like if Macbeth used the nights dagger the night should not leave such objects when knowing they should protect the King ,and by Macbeth leaving the dagger it makes it look like one of the nights did it,then Lady Macbeth by her knowing she should have turned him in or said something,because just  by her knowing what he did she is involved in the crime.