1949, the Japanese Occupation is over, Singapore has returned to British control, but the people are still struggling to pick up the pieces of their lives. 19 year-old Elizabeth Lee (Cheryl Wee) has just finished her Senior Cambridge exams
Elizabeth, Hani and Siew Lan decide to join the police, but they have obstacles to overcome. At the academy, they undergo tough training and Elizabeth gets picked on by Lucy (Melissa Faith Yeo) and other trainees.
Elizabeth and Hani are eager to catch criminals but the police force has different plans for them. Nevertheless, a serial snatch thief on a robbing spree might be the chance to prove themselves if they can nab him.
Elizabeth is partnered with the sexist Inspector Kong Say Chong (Nicholas Lee) as they investigate the chilling rape and homicide of an innocent schoolgirl. Can she endure his caustic barbs to solve the case without punching his face?
The police are overwhelmed by fierce riots breaking out across the city when a girl raised by a Malay family is ordered by the court to return to her biological parents. Meanwhile, Hani grows weary of answering phones.
The police must deal with several cases of vigilante justice meted out by an elusive female gang The Red Butterfly. Tensions rise in Ang Huay over talk of a potential successor for their leader, Kway Pek and one of the faction heads.
All eyes are on Ang Huay when the head of Tang Gu Long is found dead. To make matters worse, it is discovered that someone in Ang Huay is dealing in opium. As secrets within Ang Huay are slowly uncovered, how will its leaders manage?
As Ang Huay mourns the loss of one of its leaders, Seng Hock questions his involvement in the gang. Meanwhile, a villager makes a most grisly find - someone's drowned a baby in the well.
Illegal gambling dens continue to flourish despite the best efforts of the police. They begin an operation to stamp out corruption within the force. Seng Hock attempts to gain Dua Jiak's trust, and Hani faces a tough decision.
The cold-blooded murder of a shopkeeper sets off feelings of anger and injustice among villagers as suspicion falls on a widely-hated British officer. Meanwhile, Elizabeth tries to patch things up with Hani.
Elizabeth and Hani's relationship deteriorates further when Hani is reassigned to a rural police division and given menial tasks. The rest of the team has to handle yet another series of deadly protests fueled by anti-colonial sentiment.
A rich tai tai turns up dead on the beach, but her valuables are intact, sparking much speculation. Meanwhile, Sadeeq and Hani work together on a case of a child prostitute, Wee Han tries to match make Seng Hock with Siew Lan.
Elizabeth and Siew Lan meet cabaret dancer Mona Fong again, under different circumstances. Meanwhile, a gang of robbers are exploiting the frequent blackouts across Singapore to strike terror. Elizabeth investigates an opium dealer.
A nervous young man surrenders himself at the police station to confess to a killing, but it turns out to be more than the police expected. Meanwhile, Seng Hock makes an important discovery at Elizabeth's home. Sadeeq has a date.
Yoke Lien becomes concerned when San Gu starts participating in an illegal lottery. Seng Hock makes an important discovery that points to betrayal within his gang. Kway Pek celebrates his birthday, but Dua Jiak has sinister plans.
Fate deals a crushing blow on Siew Lan. Meanwhile, a girl and her parents press charges against her doctor for rape and his denial is absolute. Hani helps Graham in his time of need and Siew Lan pursues matters with Elizabeth's help.
Yoke Lien decides to tell Elizabeth about her past. The police deal with the return of legendary kidnapper Lam Kee Fong, and Ang Huay elects a new leader. Who will rise up to take Kway Pek's place?
In the season finale of Mata Mata, Elizabeth fights for her life in Ipoh, Hani advances into enemy territory and Siew Lan treads the thin line between justice and vengeance. Meanwhile Seng Hock faces off his most formidable adversary.
