The story begins with Hong Siu Lung (Louis Koo), a G4 officer who just broke up with his girlfriend Chun Ching (Sonija Kwok) due to his hesitation in getting married despite their seven-year relationship. When she decided to marry someone else, he became depressed.
At that moment, a weird scientist whom Siu Lung rescued earlier kept stalking him. He took Siu Lung to his secret lab and showed him the time machine. He even asked Siu Lung to help him with his time-travelling experiment.
Siu Lung refused at first, but later he's willing to be the lab rat because they promised him a chance to start over with his girlfriend once he returned. They planned to send him back more than 2000 years in time to capture the moment of coronation of Ying Ching (aka Qin Shi Huang). They picked Siu Lung for this experiment because of his resemblance to one of the terracotta warriors.
Before he left, they gave him a little machine and told him to go to Xianyang (capital of the State of Qin) in the year 247 BC with the machine turned on so they can track him and bring him back to 2001. The battery for the machine would last 2 years. They also gave him some supply and 2 pills for emergency use.
An error occurred when the time machine was activated, which caused him to travel back to the year 250 BC, three years prior to the actual crowning event. Siu Lung got up and realized that he was stuck in the State of Zhao during the Warring States Period.
The first person he met in this world was a female assassin named Sin Yau (Joyce Tang). When Siu Lung landed, he accidently 'rescued' her so she decided to 'spare' him despite his oddity.
Siu Lung took his machine out but it didn't seem to be working. He realized that he would be stuck here for 3 years before he can go back.
Siu Lung asked Sin Yau to help him get to Xianyang. Sin Yau explained that she first needed to take him to Handan (capital of the State of Zhao) and from there they would enter the State of Qin.
On their way, Siu Lung and Sin Yau met and rescued Yuen Chung (Yuen Wah), a powerful swordsman, from his evil junior Yim Ping. They then successfully sweet-talked him to teach Siu Lung how to wield a sword.
When Yim Ping and his men attacked them again, Yuen Chung ended up getting killed by Yim Ping when he tried to save Siu Lung.
Siu Lung and Sin Yau then killed Yim Ping. At that moment, Sin Yau gave off an evil smile. It turned out that Yim Ping was her target, so if she killed him, she can earn money. Sin Yau knew that she couldn't beat Yim Ping by herself so she lured him here and used Yuen Chung to kill him for her.
Yuen Chung died in Siu Lung's arms. Before he died, he handed Siu Lung a badge and told Siu Lung to find him a successor. Siu Lung figured out that Sin Yau was behind this. He got mad and decided to walk off without her.
And Siu Lung continued with his journey. When he stopped by a river for some water, his horse ran off. A group of men who also happened to stop by that river helped Siu Lung get his horse back. A while later, Siu Lung saw those men again and they were fighting with a group of masked people. Without asking, Siu Lung just jumped in and help those men defeat the masked people.
One of them had the mask fallen off and revealed to be a girl. The men Siu Lung helped turned out to be bandits. Siu Lung realized that he had helped the wrong people. To save the remaining two people (including the girl) from getting killed, he suggested the bandits to capture them instead. Hence, they were taken to the bandits' place and Siu Lung followed.
They were Wu Ting Fong (Jessica Hsuan) and To Fong (Au Sui Wai). They were ordered by the Qin to send the He Shi Bi (a piece of jade) to the State of Zhao in exchange for Qin's prince Ying Ching and his mother Chu Kei, who were captured by the Zhao. On their way, they were attacked by the bandits and the He Shi Bi was robbed. Siu Lung later successfully saved them from the bandits but Ting Fong still insisted that he was a pervert.
As they escaped from the bandits' place, they realized that they hadn't retrieved the He Shi Bi yet. Siu Lung told To Fong to look after Ting Fong, while himself would return and retrieve it. When Siu Lung went back, he saw a man killing all the bandits and even took the He Shi Bi away with him.
Siu Lung and To Fong went after that man. He turned out to be Lin Chun (Kwong Wa), a trusted swordsman of the highly ranked Zhao official Chiu Muk. Lin Chun went into a jade shop and ordered a fake He Shi Bi to be made. After that, he killed the man and took the 2 He Shi Bi with him. Lin Chun probably wanted to give the fake one to his master Chiu Muk, while himself would keep the real one.
Siu Lung put some laxative into Lin Chun's tea or something, making him go to the washroom nonstop. When Siu Lung finally found his chance, he sneaked into his room and switched the 2 He Shi Bi (so right now the real one is in place of the fake one and vice versa.)
Siu Lung and To Fong then returned to Wu Ka Bo (Ting Fong's "house"). There, Siu Lung told Ting Fong's dad Wu Ying Yuen (Wong Wai) about the He Shi Bi and Lin Chun. Ting Fong insisted that he was lying and claimed that she knew Lin Chun well and he wouldn't do that. But Wu Ying Yuen decided to trust Siu Lung once because Siu Lung promised that he would handle this and that everything would be ok.
Lin Chun brought the He Shi Bi to Chiu Muk (Waise Lee). This He Shi Bi was supposed to be the fake one but since Siu Lung switched them, Chiu Muk now had the real one instead. Chiu Muk was actually a spy from the State of Chu. He ordered Lin Chun to steal the He Shi Bi to prevent the trade between the Qin and the Zhao and keep them on bad terms, which would be advantageous to the Chu.
The next day inside the Zhao palace, Zhao's king asked Wu Ying Yuen for the He Shi Bi. Siu Lung then pointed at Chiu Muk and said that the He Shi Bi was at Chiu Muk's place. He also said that it was thanks to Chiu Muk that the He Shi Bi can be safely returned to Zhao. Now that Siu Lung blurted everything out, Chiu Muk had no choice but to hand over the He Shi Bi to Zhao's king. Both Chiu Muk and Lin Chun got really pissed. Zhao's king then asked some jade expert to examine the He Shi Bi to see if it was real or not, and Lin Chun was extremely shocked to hear that it was real.
Lin Chun finally figured out that Siu Lung was behind everything. Although he's pissed at Siu Lung, he could only get along with him because after all, Siu Lung did save him from getting punished for stealing the real He Shi Bi.
One time when Siu Lung, Ting Fong, Lin Chun and To Fong went out for a drink, they saw Chiu Poon (Raymond Lam) bullying a waitress. Chiu Poon was Chiu Nga's son and Chiu Nga was Zhao king's younger sister so nobody dared to stop Chiu Poon. However, Siu Lung and Ting Fong stood up to him anyway and Siu Lung even bullied him back. Chiu Poon was humiliated in public so he got really mad and ran away.
The next day, they were at the Zhao palace again because Zhao's king wanted to thank them for bringing home the He Shi Bi. While wandering around, Siu Lung met Zhao's princess Chiu Sin (Michelle Saram). Chiu Sin was dressing up as a maid so Siu Lung didn't know that she was a princess. She was actually a friend of Ting Fong and always felt lonely so Ting Fong often visited her. Ting Fong even told her about Siu Lung, but addressed him as "pervert".
Wu Ying Yuen and Siu Lung asked Zhao's king to keep his words: let Ying Ching and Chu Kei return to Qin. However, Chiu Muk and Lin Chun said to him that he didn't have to do so because the He Shi Bi was supposed to be his in the first place and Zhao's king listened to them. He then asked for a sword fight between Siu Lung and Lin Chun to see who's better. Wu Ying Yuen suggested that they should have a "soccer" match instead.
At night, Siu Lung sneaked into the place where they kept the hostage in an attempt to rescue Ying Ching and Chu Kei. He unexpectedly met To Fong there and he took him home. When they returned to Wu Ka Bo, Wu Ying Yuen revealed that he was a Qin and his mission was to rescue Ying Ching and Chu Kei. Siu Lung then added that he was also a Qin and sent by Lui Bat Wai (a Qin chancellor) to help Wu Ying Yuen complete his mission.
Ting Fong asked Lin Chun to get her some drug that would cause temporary paralysis because she wanted to prank Siu Lung. Lin Chun purposedly got her some rat poison instead and told her that the drug wouldn't kill him. When Ting Fong was about to give the drug to Siu Lung, he discovered that it was poison. Ting Fong got mad and went to find Lin Chun. Lin Chun said that it was just a mistake and told her not to get mad at him.
Siu Lung showed everyone in Wu Ka Bo his skills in soccer. Wu Ying Yuen asked him to train the team for the upcoming soccer match and Siu Lung agreed. He came up with some 'modern' methods of training and made everyone follow him. Ting Fong also trained under his methods.