On the day of the invasion, Sokka goes over some maps of the world. Katara gives him a drink and Aang arrives and greets everyone. Katara comments that he seems well rested and Aang says now he is ready to face the Fire Lord. Toph asks him if for his strategy he is planning to use the Avatar State. Aang says he can't and explains that his last chakra was sealed when he was blasted by Azula in Ba Sing Se.
Katara sees a thick fog rolling in and asks Sokka if she thinks it will delay the invasion. Sokka smiles and says it is the invasion. Water Tribe boats emerge from the mist and, together with Toph, Aang creates some makeshift docks in the cove. Sokka and Katara greet their father Hakoda. Sokka asks about the people he requested and Hakoda says he brought them but he is not sure about some of them.
The waterbenders from the Swamp walk off the boat. Hakoda comments that they seem a little weird and Bato agrees. A voice calls out to Katara and she recognizes Haru who now has facial hair walking toward them with his father. They greet him and introduce him to Toph. Toph suddenly starts and gets into a battle stance.
Someone grabs her and she is swept into a hug by the Hippo who says he is happy to see her. She asks if they are there for a rematch and The Boulder says they are now there to battle for their kingdom. Toph smiles and says, "Sweet."
There is an explosion on one of the boats and everyone runs over to see the inventor from the Northern Air Temple pop his head up and start coughing. Teo and his father come off the boat together covered in something. Teo's dad comments that peanut sauce does not make for very good bombs.
Sokka asks if he able to finish work on the plans that he sent. Teo's dad says he was able to finish and Teo also presents Aang with a gift, a brand new Glider. Meanwhile, at the Fire Nation prison, the guard says he bets Iroh wishes he was out of the cell. Iroh has his back turned and the guard continues that he is never getting out. Another guard, Ming walks in with food for Iroh. The other guard leaves.
Ming gives him a look as he walks out and continues to Iroh. She whispers that she added some tea and pushes the tray through the bars. Iroh turns and thanks her for being kind to him while he is in prison. Back at the cove, all the warriors gather for the briefing of the mission. Sokka is nervous but everyone tells him he will do fine.
He stumbles up to the platform and trips a few times, then tries to explain the mission but starts to stutter. When Sokka starts rambling from the pressure, Hakoda goes up and tells him to take a break. Hakoda explains the mission clearly and thanks everyone for their courage.
Sokka slumps in his seat as everyone listens intently to Hakoda. After Hakoda finishes with the battle plan, The Boulder says he is confused. He asks if the point is to attack while the eclipse is going on. Hakoda then tells everyone that the eclipse only lasts for 8 minutes and they need it most when they are surrounding the Royal Palace.
He then says that at the end of the day, the Fire Lord will have been defeated and the war will be over. Everyone cheers but Sokka looks unhappy in his seat. In last preparations, Katara fills her skins with water, Toph dons an Earth Kingdom suit, and Appa appears with full armor. Aang sits at the edge of the cove and shaves his hair.
In the Fire Nation, Zuko lets down his hair and sits down to write something. Sokka sits on a ledge looking at his helmet. Aang flies up and says everyone is waiting for him. Sokka says he messed up at the invasion briefing. Aang tells him that it was not his moment of truth and it was just public speaking, which no one is good at.
Sokka turns to him and says that his father is good at it. He explained perfectly and inspired everyone like a good leader. Aang says that his moment of truth will be out on the battlefield. Sokka says Aang seems so confident and asks why he is so sure. Aang replies determinedly that he already failed the world once at Ba Sing Se.
As the boats near the Fire Nation, Bato spots the first obstacle, the Great Gates of Azulon. Hakoda tells Katara to make some fog cover with the other waterbenders. She complies and they reach the gates. Suddenly an alarm goes off and a large net is pulled up and set aflame to block their path.
Fire Nation skiffs head toward them and Hakoda orders everyone below deck. He turns to Sokka and says he hopes his invention works. The Fire Nation soldiers board but after a thorough search they find the boats deserted. Underwater, the invasion force continues in submarines.
Hakoda compliments Sokka and Toph say he has found a worse way to travel than flying. The Duke hands her his helmet and she grabs it. Sokka points out that it was just his idea, when others did all the work. Teo's dad says that he should not sell himself short. Teo's dad calls in brilliant but comments that Sokka's original drawings were a little hard to understand. He holds up a crude sketch of what looks like a fish with warriors inside.
Ming brings lunch to Iroh and he thanks her again for bringing him extra rice. He then turns serious and says she should take the rest of the day off. He says she doesn't look well and she is confused. He says she should trusts him since it would be better that he is not there in the afternoon. She looks at him for a moment then walks away.
The submarines surface to replenish their air supply. Aang joins the others on deck and says he is ready. Sokka and everyone else come forward to hug him and they all wish him luck. Hakoda tells them that break time is over and they need to get back in the subs.
The others walk away leaving Aang and Katara alone. Aang and Katara both try to speak at once and Aang lets her go first. She says that he has grown and changed a lot and she is proud of him. Aang smiles and then says that everything is going to be different after today. He looks down and asks what if he does not come back.
Katara says not to say things like that and Aang leans in and kisses her on the lips. After they break apart, Katara blushes and looks at Aang. He opens his glider and with one last look, leaps into the air. She stares after him and Sokka comes up and tells her it is time to leave. She leaps over on Appa and creates a bubble for him to breathe under water and everyone dives.
Zuko looks at a picture of himself with Mai. He apologizes to her then leaves a scroll on the bed and leaves. Aang flies over the invasion force and his stomach growls. He opens the secret compartment in the glider for snacks and eats some. He comments that maybe it was a good idea.
Hakoda at the shore and orders everyone in position. As the submarines enter the dock area, an alarm blares and the battlements start firing harpoons at the shapes in the water. One of the subs gets hit but a waterbender inside seals it with ice. It is pulled out of the water but Katara slashes though the chain and they continue.
They fire torpedoes covered in ice and use bending to blast them forcefully at the wall. They explode and create openings for the subs. Inside, all the warriors wait and Sokka sighs. The subs reach the surface and immediately come under fire from the battlements surrounding the shore. The subs hit land and open to release their tanks.
As the invasion force moves forward, the battle continues. Katara lands and Fire Nation tanks emerge. The Earth Kingdom Tanks crush a tank and a tower and move on. The swamp waterbenders also manage to take out 2 tanks. Tho wonders where Huu is as they throw a tank into the water. Suddenly, Huu's weed monster emerges and throws another tank into the water.
Du asks Huu where he was and he replies that it took a long time to gather enough seaweed. Sokka, Hakoda and other Water Tribe warriors face off against some soldiers. Sokka hitches a ride and is joined by Hakoda who takes out a group of soldiers on the way.
A battlement fires a harpoon at Teo's father who is driving a truck full of boulders. When the smoke clears the back of the truck is demolished but Teo's father is unhurt. The invasion force is having trouble moving forward though. Hakoda says they have to get rid of the battlements. Sokka says he has an idea.
They hop on Appa and fly by the battlements. Sokka slices off the harpoon and Hakoda throws in some bombs. Katara takes care of another by freezing the inside. They land and split up to two different towers. Sokka breaks through the door and Katara quickly freezes the soldiers while Sokka destroys the launcher.
They run back out and see Hakoda jump in through the launcher opening. There are sounds of fighting then a yell and a loud explosion and smoke billows out of the opening. Sokka and Katara start and Hakoda staggers out then falls to the ground.
Katara and Sokka run to him.
Zuko faces a picture of his mother and says he has made some bad choices. But today he will set things right. He puts on his sword, dons his hood and walks out. Appa flies around a corner and sets down to allow Sokka to help Hakoda to the ground. Katara pulls out water and starts healing the wound.
Hakoda says it feels better and he struggles to rise. He says he needs to go back to the troops. Katara tells him he is hurt badly and he can't fight anymore. Hakoda argues that everyone is counting on him to lead the mission. He tries to get up but falls back. Sokka asks if Katara can do anything but she says she is trying.
Sokka thinks for a moment, and then declares that he will lead the invasion. Katara is unsure but Sokka says they have no choice since the eclipse is soon. Hakoda says Sokka can do it and he is proud of Sokka. Sokka smiles, puts on his helmet and flies off with Appa.
Sokka calls to the troops and orders them to get in wedge formation. He puts the benders in the middle and says they are heading for the palace. Once everyone is in position, Sokka draws his sword and shouts: "Charge!"
Meanwhile, Aang stands on the rim of the mountain looking at the Royal Palace. He opens his glider and flies down. He walks around but finds that the entire area is deserted. He comments that it is weird and moves on. The invasion force breaks through the wall by crashing a truck with explosives into it. The tanks continue on as the soldiers steadily fall back.
Aang bursts into the throne room but again no one is there. Aang's eyes widen and falls to his knees shouting "Fire Lord Ozai, Where are you!"