Armed Reaction IV (Chinese: 陀槍師姐 IV; Jyutping: to4 coeng1 si1 ze2 IV) is a 2004 Hong Kong modern cop drama produced by TVB. The drama stars Bobby Au-yeung and Ada Choi as the main leads with Joyce Tang, Marco Ngai, Mimi Chu, Frankie Lam and Yoyo Mung in main supporting roles. Original broadcast of the series began on TVB Jade channel from February 2 till April 9, 2004 at 9:30-10:30 p.m. timeslot with 40 episodes total. The fourth and final season of the popular TVB drama series about the first Hong Kong policewomen with guns, Armed Reaction IV pits our heroines and heroes against their toughest challenges yet - both professionally and romantically! Aired to wonderful word of mouth in 2004, the 40-episode series is again produced by series creator Kong Yip Sang, and features returning stars Joyce Tang, Ada Choi, Bobby Auyeung, and Marco Ngai, plus popular new additions Frankie Lam and Yoyo Mung. The strong supporting cast includes Ha Yu, Chu Mi Mi, Angie Cheung, Mak Cheung Ching, Raymond Cho, Akina Hong, Lo Hoi Pang, Gordon Liu, and Kenneth Ma. Having won the heart of Zi , Sang decides to propose to her, but the career-minded Zi just isn't ready for marriage yet. When other suitors appear around Zi, including rich playboy Hei and Superintendent Kin , the jealous Sang breaks up with Zi after numerous conflicts and misunderstandings. Zi soon begins a new romance with Kin, and that hurts Sang deeply, but he then finds Ching from forensic department has her eye on him... Meanwhile, Sam Yuen is again pregnant with Fung's baby. Unfortunately, she is diagnosed with a disease that puts both the baby and herself in grave danger. Faced with such crisis at home, Fung also has to worry about the threat posed by a triad gang, whose leader, Wing, makes an unexpected confession of love to him! The series takes place a few months after the 3rd installment. Chan Siu Sang and Wai Ying Zi have been dating for a while and seems to be in a stable relationship. Everything seems to be looking up for Ying Zi now that she's in a stable relationship and finally got a promotion at work, but the only that she and Siu Sang seem to fight about is marriage. He wants to rush into marriage but she wants to put it off for a few years to focus on her career since it is flourishing. Their relationship is further complicated when Siu Sang becomes jealous of Ying Zi's new handsome co-worker Ken, Mad that Siu Sang does not trust her, the two decide to break up. Ying Zi soon starts dating Ken since the two grew close while working together and Siu Sang begins dating Sunnie who works at the forensic department after being pursued by her. Having gone through so many tragedies in the past Chan Sam Yuen finally decides to focus on her family as top priority. She and Ching Fung have patched up their marriage even though it is still not perfect. With a difficult pregnancy Sum Yuen is no longer focus on her career. All seems well with her and Fung when she gives birth to a son until Fung gets entangled with female triad boss Chiang Tin Wing and her husband Sing Jin Choi. Fung is in charge of the case of Wing and her crime empire. While investigating Wing, she takes a liking to Fung and drugs him so she can have her ways with him. She uses their one night of passion to blackmail Fung into continuing their affair. Choi finds out about the affair between his wife and Fung, enraged with his wife's infidelity he accidentally kills her and frames Fung for her murder. With evidence to clear Fung of the crime Choi decides to kill Fung as revenge for ruining his marriage.