Bomb disposal expert Yeung Yat-Sing, Ivan, (Kevin Cheng) returns from England to visit relatives and he comes across a grenade case by accident. Ivan's skills are highly appreciated by Senior Chemist Ko Yin-Bok, Timothy, (Bobby Au-Yeung) and he is invited to join the Forensic Division. Ivan soon becomes the division's rising star. Ivan gets back in touch with his long-lost best friend Koo Chak-Sam, Sam (Frankie Lam). Sam serves as a forensic writer and he is going to get married soon.
During a case, Sam's fiancée Lam Ding-Ding (Linda Chung) and Timothy's police girlfriend Leung Siu-Yau (Yoyo Mung) are caught in an explosion meant to kill two drug dealers. Ding-Ding dies of her injuries, while Siu-Yau loses movement in her right hand and goes half-deaf. Yau's duties are passed to Ma Kwok-Ying, Bell, (Charmaine Sheh) from the Narcotics Bureau. Both Sam and Ivan find Bell extremely charming with her smart and unfathomable characteristics in case handling.
Integrating laboratory techniques, logical reasoning, and forensic knowledge, the trio strive to fight against crimes tremendously. As they get to know each other more and more, the entangled triangle of love also starts to hinder their working relationships. Cases includes "The Skeleton", "The Case of the Disabled", "The Movie Star Mystery", and many more. The forensic scientists went through different ways to solve each of those cases.
Meanwhile, between all this, Shen Xiong ( Raymond Cho ) and Yvonne Mok ( Florence Kwok Siu-Wan) begin to fall in love with one another. One day at Shen Xiong's place, where he is determined to tell Yvonne his feelings for her, she unbuttons her shirt, saying she will keep up to the promise she made in front of all their colleagues. Trying to stop her, Shen Xiong accidentally touches her chest. When he tries to draw his hand away, Yvonne grabs it. After a while, she leans forward and kisses Shen Xiong passionately. Their colleagues find out about it eventually and for a while, Shen Xiong misunderstood somethings left at his place by Yvonne and thinks she is pregnant with his child, but this turns out to be a false alarm.
At the end of the series, Ivan and Bell end up in a car crash while chasing a fugitive, but through that experience, Ivan knows that Bell is committed to him, with her efforts to pull him out of the car in which they were trapped in. He does recover but later when getting ready proposes to Bell on a yacht another bomb explodes. In the end, Ivan suffers from an explosion by a bomb planted by a fugitive to get revenge on Bell, which leads him into a coma. Bell was greatly upset. The fugitive was tricky and tried to capture Bell at the police station. The fugitive mostly appears eating dried ginger. After the last case, Timothy and Siu Yau get married. During the wedding, Ivan wakes up, although the frame only shows Bell receiving a call on her mobile phone, then running ecstatically, while crying, from the wedding, ripping her dress as she did in the first episode to aid running. The remaining wedding crowd finds out, and runs after Bell to see Ivan.