Tianming had a nightmare about being separated from Yue-er (a foreshadowing). When he wakes up, Ge Nie realizes that the spell on Tianming has grown stronger. At night, Yue-er, Tianming and Shaoyu began their tour in the Machinery City. Shaoyu tells the others two about the Wei Zhuang and his assasins called "Quicksand" and "Reverse Quicksand". Datiechui and his two men are attacked by Yinfu in the jungle. One of the man is killed by Yinfu, the other who runs for help is killed by someone in black. Datiechui is also in grave danger.

When Yinfu is about to kill Datiechui, he is stopped by Gao Jianli. The three children arrived at a huge gate. Yue-er says the gate leads to the Forbidden Land, a very dangerous place of excecution, but the two boys don't take it seriously. With Xuenv's help, Gao Jianli wounds Yinfu badly. Wei Zhuang makes the Qin's armies clean away the traps. One of the Mohist machinery beasts, White Tiger, confronts Gongshu Family's machinery serpent. Gao Jianli believes Ge Nie has killed Jing Ke and thus suspects him to be a spy. Gongshu Chou asks for the scroll of the traps. Master Ban is attacked.

The one in black takes the key to the secret chamber. Shaoyu sends Tianming a message, asking him to meet somewhere, but Tianming doesn't know the characters. Gao Jianli sees Tianming and remembers Jing Ke. Tianming meets Gao Jianli and asks him about his father, but Gao Jianli gives no reply. The Mohists realizes someone has entered the secret chamber and taken the scroll. Tianming and Yue-er meet Shaoyu and Master Xu's Sword-founding Pool. Tianming somehow remembers he has seen the 1st-ranked sword Tianwen(Heaven Questions), the sword of Yingzheng, and knows the sword in in the Xianyang Palace. He can't clean up his train of thoughts no matter what, the spell on him attacks and Tianming goes unconscious. Yue-er decides to try treating Tianming with her inner strength.

Yue-er is about to recover Tianming when the spell begins to counterattack and poison herself. Gongshu Chou claims he has found out the fatal weak point of the Machinery City. Duanmu Rong arrives in time and saves Yue-er and Tianming. Wei Zhuang gives a tiny bottle of poison to his spy, who disguises himself as Duanmu Rong and deceives Gao Jianli who guards the Centre Pool. Master Xun sees Ge Nie doing something to the pool and is wounded. In fact, that man is the Wei Zhuang's assasin, Heiqilin(Black Kilin). He has disuised himself as the Mohist who run for help and entered the City. He puts the poison into the water which flows everywhere and gives power to the whole city. Gao Jianli tries to kill Ge Nie but Duanmu Rong stops him.

Duanmu Rong tells Gao Jianli that she has checked all the water in the City, and somehow there's no prison at all. Ge Nie is prisoned, and Tianming is furious with the Mohists. Xuenv immobilizes him and put him into the room next to Ge Nie's. Duanmu Rong gives the Mohists leaders her unique pills that can resist any prisons for four hours just in case. At the daybreak Duanmu Rong is suddenly reminded of a poison called One Thousand Nights, the poison that never attacks unless it's exposed to sunshine. The poison became gas and the whole City is paralysed. Tianming feels painful because of the gas, and Ge Nie tries to teach him to resist. Wei Zhuang and Qin's armies began their attack.

Shaoyu and Yue-er put on protective scarfs and go through the poisonous air. They run into Heiqilin but survive by playing dead. Tianming climbs across the cliff to Ge Nie's window, Ge Nie wonders why he is not affected by the gas. Ge Nie tells him to climb to the corridor about 110 metres away. Tianming is frightened. Duanmu Rong finds Shaoyu and Yue-er, they go to Ge Nie and they're unable to set him free. Tianming has a hard time over the cliff, and alomst gets killed by the trap beside the corridor, but Shaoyu saves him by resisting the machine with his hands. Tianming now understands Ge Nie's words, and yells to tell him to take care.

Duanmu Rong sees the broken jade that Tianming wears and suspects the jade to be a royal item. They run into the Qin soldiers and fight with them. The poisoned Mohists are no match for the army. Gao Jianli shows up and kills Canglang. Wei Zhuang beats Gao Jianli but doesn't chase the Mohists. Duanmu Rong finds it impossible to meet the other leaders, so she sends the children into the Forbidden Land. Herself is captured by Yinfu. The other leaders gather in the Mohist Core, the only place free from Wei Zhuang. Wei Zhuang sends soldiers into the Central Rotunda to try the traps, and all of them are killed.

Gongshu Chou shows Wei Zhuang a machinery man made of Wushuang's body. This human machine cleans away all the attacks from the traps. Wei Zhuang captures many Mohists and threatens to kill them one by one if the leaders don't surrender. In the Forbidden Land, the first level is called Tiger Leap, the player must have extraordinary strength and kong-fu to pass. The three pass the level thanks to Shaoyu. The leaders get awareness of the children's acts by watching the movement of the machines. At the second level Monkey Swing, when Tianming tries to pass the abyss, Shaoyu somehow drops Tianming's safety rope. Both Tianming and Yue-er are falling into the abyss.

Shaoyu actually has acrophobia because of childhood accident, but at the last moment, he gets over his fear and catches his two friends. Tianming manages to pass the level and open the road that leads aross the abyss. The children see the murals about Jing Ke assasining the Qin Emperor. Shaoyu tells the story that no one survives Jing Ke's attack, but it's a mystery why the emperor survives. Chilian uses her poison to torture Duanmu Rong. Rong and the other Mohists gesture that they'll kill themselves if their friends try to rescue them. The three fall into a trap with rotating blades around them, and a fabulous music box in front of them.

The Music Box is the tresure of Yin-yang School, and it was somehow taken to Mohist School. The children realize they have to pass the test of the box to survive. A starry sky appears above them, and Yue-er finds out part of the secret with her knowledge about the Five Elements, the Twelve tones and Five sounds. She remembers how her mother has taught her to watch the stars, and find the vital star, the key to the test. Yue-er takes the box with her when they leave. Gongshu Chou manages to enter the Forbidden Land. The children come to a place with two roads. When they go to read the words separately, Shaoyu stands at the entrance to the Kingly Path, Tianming and Yue-er at the Chivalrous Path.

The original road suddenly cllapses and the three have to separate. Shaoyu walks into a chamber and the trap forces him to play a chess game, not the Go chess game in which the chessmen kill each other, but a reversi chess game in which the chessmen turns enemies to friends. Shaoyu was proud of his chess skill, but after a while he loses his priority and his life is threatened by the trap. He recalls his father's death on the battlefield, and tries his best to win the game. He finally wins the game and a weird weapon shows up before him.

The inscription on the weapon reads Pozhen Bawang Qiang (The overlord's spear that crushes armies). Shaoyu is very fond of this reward. Tianming and Yue-er enters a chamber where there are many bronze soilders and a huge bronze god. Suddenly the bronze men began to attack them. Yue-er realizes that the bronze god knows their locations through the weight on the floor tiles. Therefore she stands on her tiptoe at the border of the tiles. Tianming pulls the key to the back door from the bronze god, and they manage to pass the chamber. Yue-er finds the key to be the ultimate weapon of Mohist, Feigong(No War).

Tianming somehow finds the way to transform Feigong into all kinds of weapons. Gongshu Chou operates the machines and traps the three children, but himself is also sent into the prison that Tianming and Yuer falls into. Gongshu Chou claims to be a friend of Master Ban. He tells Tianming about the sword painted on the ground, the Broken Rainbow. This sword was the one Jing Ke used to assasin Ying Zheng. After Jing Ke died, Ying Zheng Broken Rainbow reforged as Rainbow Abyss and granted it to the person who killed Jing Ke. Tianming is shocked to know Ge Nie has killed Jing Ke.

Gongshu Chou opens a door on the ground and says someone has to swim in the underground river to the Waterfall and turn on one of the Four Holy Creatures, Xuanwu(the Balck Turtle) to bring in clean water or they will all die. He tells Tianming to rotate on the red handle, but when Tianming makes it to the Machine Creature, he realizes something wrong with Gongshu and rotates the black one. Clean water is brought in but Tianmign is attacked by the Black Turtle. Mohists realizes Wei Zhuang has set a trap for their appraoching allies and sends Daozhi to warn them. Wei Zhuang sends Baifeng to chase him.

Trapped in deep water, Tianming loses conciousness. He finds himself in a palace-like place, where a parrot yells "you're back" and his jade becomes complete. He recalls everything he has experienced: Gao Yue's story, his dream about finding his father, the assasins and villains, Ge Nie, the Mohists. He struggles in his mind and desperately wants to become strong to protect those he loves. He hears a woman's voice saying "Don't be afraid, my child. Be strong."

Tianming breaks out of the trap and sees Gongshu Chou and Yuer. Gongshu Chou fails to kill Tianming and gets punched into the water. Qin's armies chases Tianming and Yuer', they manages to defend and counterattack with Feigong. After running to a safe spot, they meet Shaoyu, who has broken off the trap. Baifeng chases Daozhi with numberless birds. After running a longway at a lightening speed, Daozhi is caught up and wounded. The three children comes to help him escape driving a White Tiger, but Gongshu Chou shows up in his machine serpent and Baifeng leaves safely.

Tianming, Shaoyu and Yuer fights Gongshu Chou in a valley, and manages to destroy the serpent using the rocks. They hurry back to the City to help the others. At the same time, Heiqilin sticks the machine and stopps the door from closing. Datiechui, Xuenu and Gao Jianli has no choice but to confront Quicksand directly. Tianming and Yuer runs into Yueshen, she finds Yuer somehow able to resist her magic so she takes Yuer away. Wei Zhuang is about to kill Duanmu Rong when Ge Nie shows up.

Ge Nie and Wei Zhuang first met each other as schoolmates when they were 18 or 19. Wei Zhuang once lost the first battle with his senior, but he has become much stronger now. During the fight, Duanmu Rong protects Ge Nie from Baifeng's attack with her own body and gets badly wounded and almost dies. She recalls her mastress telling her never to love a swordman, but she has loved Ge Nie. When she hears Ge Nie still address himself as "Zaixia"(a polite and indifferent way of saying "I"), she weeps sadly. She tells Ge Nie in her heart to protect himself for he always gets himself hurt(physically and spiritually) and closes her eyes. Ge Nie is injured because of his anger. Tianming arrives and Ge Nie asks Tianming to stand behind him, but Tianming suddenly stabs him with a dagger.