getting away with murder isn't going to be as easy as he first thought. He turns his suspicions towardMacduff, who failed to appear at the banquet. Macbeth is growing in agitation and apprehension, and it is at this point that power begins to shift away from him. This is a turning point because in the scenes that follow, Macbeth is portrayed as a man who is growing increasingly desperate and unhinged.

One could argue that the climax arrives slightly later in act 3, scene 4. After Lady Macbeth has sent away all the dinner guests, Macbeth points out the fact that Macduff did not come, despite the fact that Macbeth commanded him to be there. He also says,

I am in blood
Stepped in so far that, should I wade no more, 
Returning were as tedious as go o'er.  (3.4.142-144)

At this point, Macbeth figures that he's already gone so far to procure the throne and, more recently, to keep it, that he might as well continue onward. He seems somewhat resigned to a bloody and violent future. He calls the idea of continuing forward "tedious," implying that he is somewhat indifferent to it; at least, he doesn't feel very strongly.  Earlier, in act 3, scene 2, Macbeth seemed anything but indifferent. He said, "Oh, full of scorpions is my mind, dear wife!" (3.2.39) He even implies that it would be better to be dead than to be as anxious and tortured as he feels:

Better be with the dead,
Whom we, to gain our peace, have sent to peace,
Than on the torture of the mind to lie
In restless ecstasy. (3.2.22-25)

Macbeth felt so tortured that he almost wishes for death rather than continue on, feeling tortured. But at the end of act 3, scene 4, however, we see a turning point: Macbeth no longer feels ambivalent or pulled in two directions; he is no longer tortured about how to proceed or what to do. He seems to give in to his evil side, and this dictates his actions from here on out (actions like having the innocent Lady Macduff and her children murdered).

The climax of the play takes place in Act Three, Scene 3, when Macbeth's assassins successfully kill Banquo but are not able to murder his son, Fleance. Up to this point in the play, everything has gone the way Macbeth has planned. However, when Fleance avoids being murdered by fleeing from the assassins, Macbeth's mental stability and fortune begin to take a turn for the worse. In the next scene, the assassins tell Macbeth that Banquo is dead, but his son was able to escape. Macbeth then comments that his fears have returned and he feels uncertain about his future. Macbeth then attends a feast where he sees Banquo's ghost. Macbeth's hallucinations are a result of his guilty conscience and declining mental stability. Fleance's escape is essentially the beginning of Macbeth's downfall. From this point in the play, Macbeth's life spirals out of control, and he begins to lose his grip on reality. 

In the sense of the true Elizabethan 5 Act play format, the point of conflict in act III is the point when the central character has a significant shift in power. Since Macbeth is our central character, we are looking for the point in act III that his power stops growings. This single point is most likely the killing of Banquo while Fleance escapes. It is after this point that Macbeth becomes paranoid enough to begin seeing ghosts. Although he had doubted his actions immediately after killing Duncan in act II, he still believed in the witches' prophecies until he realized that Banquo's prophecies would probably also come true.

As in most of Shakespeare's plays, he does a great job of wrapping up all the elements of plot in the fifth act. At the conclusion of Macbeth, the tyrant has been executed, the kingdom has been restored, and Macduff's family has been avenged. There is much more to the conclusion than just the events, though. In Act 5, we also see the conclusion of several images and themes developed throughout the play. The theme of appearance vs reality, and the motif of equivocation, is brought to a close as Macbeth realizes the truth of the witches' prophecies. The repeated images connecting blood and guilt are brought to a close through both the death of Macbeth and the suicide of Lady Macbeth. Through each of these conclusions, Shakespeare is able to demonstrate the disconnect what people perceive to be true and what is actually true, as well as show the very real consequences for rebelling against the natural order of life.

Most Shakespeare scholars believe that the conclusion, resolution, or denouement of Shakespeare's Macbeth occurs in act 5, scene 8, after Macbeth is killed by Macduff.

When they first meet on the battlefield in act 5, scene 8, Macbeth and Macduff fight, but Macbeth belittles Macduff for not being able to kill him.

MACBETH. Thou losest labor.
As easy mayst thou the intrenchant air
With thy keen sword impress as make me bleed:
Let fall thy blade on vulnerable crests;
I bear a charmed life, which must not yield
To one of woman born (5.8.11–16).

Macbeth is referring to the prophecy he heard from one of the apparitions he saw in act 4, scene 1.

SECOND APPARITION. Be bloody, bold, and resolute; laugh to scorn
The power of man, for none of woman born
Shall harm Macbeth (4.1.87–90).

Macduff responds with words that strike fear in Macbeth's heart.

MACDUFF. Despair thy charm,
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother's womb
Untimely ripp'd (5.8.15–20).

In other words, Macduff was born by Caesarian delivery, and is technically "not of woman born," as the Apparition foretold. Macbeth then refuses to fight Macduff, but Macduff ridicules Macbeth and goads him into fighting him.

MACDUFF. Then yield thee, coward,
And live to be the show and gaze o’ the time.
We'll have thee, as our rarer monsters are,
Painted upon a pole, and underwrit,
“Here may you see the tyran” (5.8.27–31).

Macbeth replies that he won't bow to Malcolm, and no matter what's happened with regard to the apparitions' prophecies about Birnam Wood and Macduff not being "of woman born," Macbeth is determined to fight to the death.

MACBETH. I will not yield,
To kiss the ground before young Malcolm's feet,
And to be baited with the rabble's curse.
Though Birnam Wood be come to Dunsinane,
And thou opposed, being of no woman born,
Yet I will try the last. Before my body
I throw my warlike shield! Lay on, Macduff,
And damn'd be him that first cries, “Hold, enough!” (5.8.32–39)

They fight again, and this time, Macduff kills Macbeth.

At this point in the "First Folio" edition of Macbeth, Macduff and all of the soldiers leave the stage—Macduff leaves under his own power, and Macbeth is apparently dragged offstage—and there is a short scene with Malcolm, Siward, and Ross. This scene is followed by the return of Macduff and his soldiers, with Macduff carrying Macbeth's severed head.

This short scene is often cut from theatrical productions of the play since it's anti-climactic to have the major combatants leave the stage for the short scene and then return, and also because there are staging problems associated with Macbeth's severed head.

In many productions of Macbeth, Macbeth is killed onstage by Macduff, then Malcolm immediately enters the stage, without the intervening short scene.

The action of the play is resolved when Macduff proclaims Malcolm king, and Malcolm give a short, conciliatory speech reuniting the people of Scotland under his rule.

As was mentioned in the previous post, Lady Macbeth is introduced as a fierce, ambitious woman who encourages her husband to assassinate King Duncan. Lady Macbeth not only devises the plan to murder the king but also participates in the plot by placing the bloody dagger back into Duncan's chamber. Initially, Lady Macbeth is unwavering in her ambition and ridicules her husband for feeling guilty. She tells Macbeth,

"A little water clears us of this deed. How easy is it, then! Your constancy hath left you unattended" (Shakespeare, 2.2.67-69).

Lady Macbeth is initially viewed as mentally strong, determined, and nefarious. However, Lady Macbeth begins to gradually lose her mind as she is overwhelmed with guilt. By Act Five, Lady Macbeth is sleepwalking and hallucinating. While Macbeth is preparing for war, Lady Macbeth wanders the halls at night and continually rubs her hands as if she is trying to wash them. The Doctor witnesses Lady Macbeth say,

"Out, damned spot! Out, I say!—One, two. Why, then, ’tis time to do ’t. Hell is murky!—Fie, my lord, fie! A soldier, and afeard? What need we fear who knows it, when none can call our power to account?—Yet who would have thought the old man to have had so much blood in him" (Shakespeare, 5.1.25-29).

In Act Five, Scene 5, Macbeth learns that his wife has died. Later on in the play, Malcolm mentions that Lady Macbeth may have committed suicide. He says,

"Of this dead butcher and his fiendlike queen, who, as ’tis thought, by self and violent hands took off her life" (Shakespeare, 5.8.71-73).

Lady Macbeth ends up becoming overwhelmed with guilt and essentially loses her mind. She goes from being an ambitious, determined woman to a guilt-ridden, mentally ill queen. 

The climax is known as the turning point of the story for the main character, who is Macbeth.  His shift in power occurs in Act III.  He has ordered the killing of both Banquo and his son, Fleance.  In the banquet scene, he sees the ghost of Banquo, which signifies his guilt--and the knowledge that Fleance escaped makes him even more paranoid.  This is the point where he realizes that the witches' prophesies have not only come true for him, but WILL come true for Banquo's sons as well.  He becomes completely ruthless at this point, and kills Macduff's entire family without any guilt/remorse.

So, the resolution would then have to be how he is defeated by Macduff.  Macbeth finally is overthrown.

Macbeth ends with the battle at Dunsinane Castle, where Macbeth has holed up awaiting the attack from Malcolm, Macduff, and the English forces. We know that Macbeth is in desperate straits, and the few that are fighting for him are of doubtful loyalty:

....none serve with him but constrained things
Whose hearts are absent too. (Malcolm, Act V Scene 4).

However, he still has the emotional reinforcement of the prophecies given him by the Three Witches in Act IV Scene 1: that "none of woman born" will harm him, and that

Macbeth shall never vanquish'd be until
Great Birnam Wood to high Dunsinane Hill
Shall come against him.

The second of these assurances is the first to be destroyed: Malcolm's army decides to use branches of the wood as camouflage:

Let every soldier hew him down a bough,
And bear't before him: thereby shall we shadow
The numbers of our host, and make discovery
Err in report of us. (Act V Scene 4)

Macbeth learns of this to his horror in Act V Scene 5:

I pull in resolution and begin
To doubt the equivocation of the fiend
That lies like truth. “Fear not, till Birnam Wood
Do come to Dunsinane,” and now a wood
Comes toward Dunsinane.

However, he still has one prop to lean on: he will not be killed by any man of woman born. It is only on the battlefield itself that this is pulled away from him, when Macduff faces him and declares,

Despair thy charm,
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother's womb
Untimely ripp'd. (Act V Scene 8)

This resolves the chief lingering question of the play, how the prophecies are to be reconciled with Macbeth's defeat, in an ingenious way -- both turn out to be true, in a way that Macbeth did not suspect.

After Macbeth is killed off-stage and his head brought on in proof, there is a short dénouement or "tidying-up," which takes the form of Malcolm's concluding speech. Here, he confirms that Lady Macbeth has killed herself and declares his intention to recall exiles and generally conduct himself in an exemplary way after being crowned King, signaling the return to normality after the abnormal events chronicled in the play:

....what needful else
That calls upon us, by the grace of Grace
We will perform in measure, time, and place, (Act V Scene 8).

Thus, Macbeth ends with the resolution of the puzzle posed by the last prophecies of the Three Witches, the disposal by death of Macbeth and his wife, and the return of all things to their normal and natural state.

The play begins with King Duncan naming his son Malcolm as king. Macbeth kills Duncan and usurps the throne. In trying to keep the throne, Macbeth turns into an evil king, killing anyone who might threaten him, including Macduff's family. Macbeth thinks he is immune from anyone "born of a woman" killing him. Thus, he thinks he is safe in any battle. The ironically satisfying ending comes when Macduff announces he was came into the world by Caesarian section, not a normal birth. Macduff is able to kill Macbeth and restore Malcolm, the original heir, to his father's throne. Thus the play comes full circle, evil is defeated, and good restored to Scotland.

You have several stories going on here--Macbeth's plans, Lady Macbeth's life and plans, Macduff's plans, the witches' plans, the state of Scotland. 

For me, the biggest turning point is when Macbeth willingly decides to seek out the witches again and they give him the apparitions he demands.  We know from a prior scene with Hecate that they will make these apparitions seem to be in Macbeth's favor, but that he will misinterpret them and this will be his final downfall.  His character change is complete at this point and he is traveling at "full speed ahead and damn the torpedos" attitude--regardless of what happens.

It could be argued though, that the climax is when Macbeth sees the ghost of Banquo.  This is the beginning of his guilt and of his physical downfall in the play.