What was Lady Macbeth's murder plan?
Lady Macbeth's plan is to get King Duncan's two chamberlains quite drunk, so drunk that they basically pass out and are unable to remain conscious, let alone actually guard him. Then, she will remove their daggers and lay them at the ready so that Macbeth can find them; this is why she is so sure that Macbeth "could not miss 'em" (2.2.12). At this point, Macbeth will creep into the room and use the chamberlains' weapons, stabbing Duncan to death. Next, Lady Macbeth plans that he will smear Duncan's blood all over the grooms as well as replace their daggers so that Duncan's two men will be properly framed for the murder and there can be no doubt about who committed regicide.
However, Macbeth, in his horror at the act, forgets to leave the daggers in the room with the grooms, and Lady Macbeth actually has to go back in herself and smear Duncan's blood on them. Next, she plans for herself and her husband to go quickly to bed and appear to be shocked when others "discover" Duncan's lifeless body in the morning. Macbeth messes this up, too, when he kills the grooms who they have framed for the crime.
Lady Macbeth says she'll wait until Duncan goes to bed (he'll be tired) and she'll make sure to give the two guards enough wine to make them sleep heavily. That way Macbeth will be able to sneak past them to kill Duncan with the two guards' daggers. Then they'll place them with the sleeping guards.
"When Duncan is asleep--
Whereto the rather shall his day's hard journey
Soundly invite him--his two chamberlains
Will I with wine and wassail so convince
What cannot you and I perform upon
The unguarded Duncan? what not put upon
His spongy officers, who shall bear the guilt
Of our great quell?"
The plan was to wait till Duncan went to bed, get the guards drunk and passed out and then Lady Macbeth would go and kill Duncan by using the dagger, yet he reminded her of her father so she couldnt and Macbeth ended up killing Duncan and the guards
He and Lady Macbeth plan to get Duncan’s two chamberlains drunk so they will black out; the next morning they will blame the murder on the chamberlains, who will be defenseless, as they will remember nothing. While Duncan is asleep, Macbeth stabs him, despite his doubts and a number of supernatural portents, including a vision of a bloody dagger. When Duncan’s death is discovered the next morning, Macbeth kills the chamberlains—ostensibly out of rage at their crime—and easily assumes the kingship. Duncan’s sons Malcolm and Donalbain flee to England and Ireland, respectively, fearing that whoever killed Duncan desires their demise as well.