EU Sergeant LING SUN-FUNG leads her EU team members to go on patrol until midnight, and for the sake of her team members' health, she even changes the menu of their meals on her own initiative. In an effort to hunt down suspects, SUN-FUNG leads her team to arrive at a walled village, where they are obstructed by the village chief, KWAN TING-MING, and his men. During the meeting, LEE SIR reports that some security employees were injured by the suspects, and SUN-FUNG reiterates that they would have captured the suspects had they not been obstructed by TING-MING. SUN-FUNG's boyfriend KWOK SHEUNG-CHING intends to propose marriage to SUN-FUNG while walking her home, suddenly, they hear thunder rumble in the sky. The following day happens to be April Fools' Day, so SUN-FUNG's younger brother, SUN-KWONG, carries out the tradition to play a prank on SUN-FUNG.… ...

After waking up in the morning, SUN-FUNG finds things turn out to be exactly the same as those that happened on April 1st. SUN-FUNG recalls the time when LING HOI quarreled with HAU-KUEN the day before, so she deliberately prevents them from meeting each other. On top of that, she even tells LING HOI to go travelling in hopes of helping him evade the disaster. Upon her arrival at the bar, SUN-FUNG spots the wanted criminal named LAT, so she promptly calls for backup. Finding himself besieged by the police with nowhere to escape, LAT instantly takes a minibus passenger hostage, surprisingly, SUN-FUNG discovers the hostage turns out to be LING HOI. SUN-FUNG thinks travelling through time back to April 1st could alter their destiny, yet things take an unexpected turn, to which SUN-KWONG explains as the "butterfly effect".… ...

After discovering a hidden camera in the windmill given by TING-MING, LING HOI becomes so angry that he immediately goes to argue with TING-MING. Suddenly, SUN-FUNG has an inspiration and tells the other police officers that LING HOI has mental health problems, hoping to keep him in the detention center for one night. Knowing that SIU-MEI will be kidnapped, SUN-FUNG cannot make up her mind whether to save her or not, but SUN-KWONG urges her not to stand by and do nothing. SUN-FUNG instructs the police officers to go on standby at the warehouse so as to prevent a shooting from happening, without knowing that SHEUNG-CHING out of the blue shows up, exchanging fire with the criminals. The criminals manage to escape, even though they are attacked by the police from all sides. Unfortunately, LING HOI still cannot escape his destiny.… ...

SUN-FUNG is eager to save LING HOI and alter destiny, but has no idea how to do it. Taking advantage of the ancestral worship ceremony, SUN-FUNG tells all the police officers to go on standby at the ancestral hall by using the excuse of having free food. TING-MING does not show up because he is otherwise occupied. It turns out that CHI-TING has been following him, above which she even spots him meeting up with HAU-YUET. With a truck approaching the police roadblock set up by SUN-FUNG, the criminals suddenly start shooting, engaging in fierce combat with the police. SUN-FUNG reveals her ability to time travel to SHEUNG-CHING, who however does not believe her. CHI-TING not only tells SUN-FUNG about TING-MING's background but also his relationship with HAU-YUET. TING-MING returns home and knows there is a power failure, so he tries to find a flashlight but passes out after getting a severe, sharp pain in his head.… ...

SUN-FUNG disappears, and SHEUNG-CHING and the others try to reach her by phone but to no avail. Recalling that SUN-FUNG mentioned about the exchange of gunfire at a logistics company, SHEUNG-CHING together with other police officers rush there, but LAT still manages to escape after an exchange of gunfire with the police. Eventually, SUN-FUNG returns home safe and sound, so SUN-KWONG asks her how come LING HOI is able to escape death. Unexpectedly, shortly afterwards, she hears LEUNG-TIM being murdered. In an effort to prevent LEUNG-TIM from being killed, SUN-FUNG decides to travel back in time to April 1st. After waking up, she goes to inform LEE SIR where the exchange of gunfire is going to take place, however LEE SIR does not believe her. Outside of the police station, SUN-FUNG sees LEUNG-TIM talking to a female flight attendant, which makes her suspect the latter has something to do with the death of LEUNG-TIM.… ...

SHEUNG-CHING finds SUN-FUNG's necklace and comes to realise that she has been buried alive. SUN-FUNG who was in a coma, later regains her consciousness at the hospital, and she runs into KING-WAI outside of her ward. It turns out that KING-WAI is looking after his wife, TSI-CHING. Predicting that LEUNG-TIM will be murdered, SUN-FUNG rushes to his home and indicates that he still has feelings for APPLE, however LEUNG-TIM has no idea what she is talking about. At that moment, LEUNG-TIM's girlfriend dashes out of the kitchen in an attempt to kill him. Suddenly, SUN-FUNG's phone rings and the person on the other end turns out to be TING-MING, who is interrogating an undercover police officer. Trying to save the undercover cop, SUN-FUNG decides to travel back in time for the fourth time.… ...

CHIN-CHEUNG is going to contact a new buyer called BROTHER PO, ahead of which he tells TING-MING to go there first, scouting out the area. SUN-FUNG tails after TING-MING in front of the hotel where they are going to do the trade, and she also tells CHI-TING to pay attention because whoever calls her is the undercover cop. SUN-FUNG follows TING-MING to a bar, but is discovered by TING-MING, who even warns her not to follow him anymore. At the hotel, CHI-TING runs into CHIN-CHEUNG in the elevator, and CHIN-CHEUNG instantly has his guard up. In the meantime, SUN-FUNG receives an anonymous call, informing her that something will happen to CHI-TING. Using an excuse of borrowing some albums, CHI-TING comes to SIU-MEI's home in an attempt to probe into CHIN-CHEUNG's background, without knowing that CHIN-CHEUNG suddenly returns leaving CHI-TING no other choice but to hide in the closet.… ...

SUN-FUNG keeps her time travel journal in order to avoid missing any details; whereas TING-MING and SIU-KEI are lost for words after learning from the news that LAT and his associates have been arrested by the police. TING-MING meets up with LAU SIR and informs him about the upcoming deal with BROTHER PO, so LAU SIR gives TING-MING an eavesdropping device. TING-MING returns to his former company to visit NATALIE, during which he asks her about things with regard to HAU-YUET. At night, seizing the chance when CHIN-CHEUNG asks for more beer, TING-MING secretly plants the eavesdropping device in the ice bucket, unexpectedly the device is later discovered by CHIN-CHEUNG. The villagers besiege CHIN-CHEUNG's office and accuse him of deceiving them, adding that they will sue him to seek compensation.… ...

TING-MING sees HO-YUEN's dead body, and CHIN-CHEUNG tells him that going undercover will only end up like this. TING-MING reveals to SUN-FUNG that he works with law enforcement, but not as an undercover cop, and he even shows her the video he secretly filmed in CHIN-CHEUNG's study room. On top of that, TING-MING suspects that the one whom CHIN-CHEUNG contacted via text message is actually the corrupt cop. During the land acquisition process, the government employees face huge resistance from the villagers, suddenly, TING-MING dashes out, vowing to join forces with the villagers to safeguard their homeland. In order to settle the matter, CHIN-CHEUNG and MR CHOW put forth a proposal to increase the compensation fund. SUN-FUNG arrives at the hospital and learns of TSI-CHING's death, so she immediately asks KING-WAI why. Reaching TING-MING by phone, SUN-FUNG tells him that CHIN-CHEUNG is going to find out who is the mole.… ...

While LAT is aiming at SUN-FUNG and about to shoot her, SIU-KEI out of the blue dashes out on a motorcycle. CHIN-CHEUNG and BROTHER PO are discussing business at a massage spa; whereas outside of the spa, TING-MING is thinking about the whole thing over and over again, and the more he thinks about it the worse he feels. HO-YUEN attempts to kill TING-MING, but is knocked out by a stun gun. After HO-YUEN regains his consciousness, TING-MING accuses him of being the mole, without knowing that SIU-MEI and a photographer suddenly show up. Right away, HO-YUEN seizes the opportunity to take SIU-MEI hostage. CHIN-CHEUNG highly recommends TING-MING for the position of Sam Heung Township Committee Convener, and all the other villagers have no objection, except UNCLE HENG, who seems to harbor a resentment. TING-MING arranges for BING-YAN to meet up with UNCLE HENG in the hope of improving the land acquisition process.… ...

TING-MING finds himself back to April 1st again after waking up. All of a sudden, SUN-FUNG appears in front of TING-MING, asking him how come there was an explosion prior to their time travel and SUN-KWONG was injured as a result of the explosion. KWUN-HUNG and HO-YUEN give a petrol bomb to HAU-KUEN and his associate and urge them to set fire to UNCLE MAU's house to burn it down. However, they are hindered by a neighbour before igniting the fire, and they end up throwing the bomb in GRANNY SAM's home. After questioning them, TING-MING comes to realise the cause of the explosion. SUN-FUNG requests SHEUNG-CHING to follow SUN-KWONG, yet she later finds there is nothing wrong with him. After SIU-KEI and the others capture HONG, HONG thinks they are going to once again force him to sell his small house concessionary right but to his surprise, it turns out that TING-MING wants to apologize to him.… ...

HONG is determined to set off a bomb regardless of SUN-KWONG's repeated persuasion against it. SUN-FUNG and TING-MING arrive at a barbecue place, where they carry out a search, suddenly someone carries a backpack and leaves. Seeing the situation go far beyond his control, SUN-KWONG promptly informs SUN-FUNG about it, without knowing that HONG suddenly sets off the bomb. KING-WAI and TSI-CHING move to a new place, but TSI-CHING is afraid that they cannot financially afford this. Out of the blue, CHIN-CHEUNG calls KING-WAI and claims that the new house is a gift from him to them. Following their meeting with the villagers, CHIN-CHEUNG and BING-YAN are about to leave, suddenly TING-MING discovers there is a bomb on the vehicle. CHING-YIN invites BING-YAN out to meet her, during which they cannot help reflecting bygone days.… ...

TING-MING arranges for BING-YAN to meet up with UNCLE HENG, hoping that he is going to stop cooperating with CHIN-CHEUNG. Revisiting the place they have been to before, TING-MING begs HAU-YUET to give him a second chance to start anew, to which HAU-YUET feels moved. Following CHING-YIN's disappearance, LING HOI goes to find BING-YAN in an attempt to get even with him. The two even fight with each other, which ultimately results in BING-YAN's death. With LING HOI being taken into police custody, SUN-FUNG urges her father, LING HOI, to recall what exactly happened, yet LING HOI only remembers that he was drunk. SUN-FUNG goes back to the power transmission tower and intends to travel back through time again to save her father, during which she runs into TING-MING. As for CHI-TING, she goes online to check BING-YAN's background, and learns that the latter has a short temper.… ...

Ever since she met BING-YAN again, CHING-YIN has been troubled by this past relationship. SUN-FUNG receives a phone call from TING-MING, telling her there is an emergency. It turns out that TING-MING has been keeping an eye on KING-WAI, whom he claims to be the corrupt cop, however, SUN-FUNG does not believe him. After learning that SIU-MEI is drunk, CHI-TING picks her up and brings her home, and she even seizes the opportunity to sneak into CHIN-CHEUNG's study room, without knowing that CHIN-CHEUNG suddenly sneaks up behind her. Trying to figure out KING-WAI's intentions by having a conversation with him, SUN-FUNG suspects that KING-WAI installed a spyware app on her mobile phone, so she immediately tells CHI-TING to help deal with it. SUN-FUNG wants to make KING-WAI give himself away, so TING-MING comes up with an idea which is to use HO-YUEN as bait.… ...

Seeing SHEUNG-CHING and CHIN-CHEUNG have a dispute, CHI-TING has to tell CHIN-CHEUNG to leave first. SHEUNG-CHING lunges forward to grab CHI-TING into his arms, hugging her tightly, without knowing the whole scene catches TING-MING's eye. SUN-FUNG is certain that CHING-YIN is going to run into BING-YAN on her way to pay tribute to her ancestors, so she hastens to the ancestral hall, but midway through, she hears that LING HOI attempted to kill himself by jumping into the sea. With SUN-FUNG and SHEUNG-CHING getting ready to escort HO-YUEN somewhere, SUN-FUNG has been keeping her guard up the whole time to see when KING-WAI is going to kill him. Later on, after discovering that HO-YUEN jumped off the building at the police station, SUN-FUNG cannot help accusing KING-WAI of committing murder in broad daylight there, to which KING-WAI not only denies but also reprimands SUN-FUNG for being too nosy.… ...

SUN-FUNG goes to CHI-TING's home, seeking to find out about what happened between her and SHEUNG-CHING, and she leaves in a huff after learning about their one-night stand. Instantly, SHEUNG-CHING who was hiding, dashes out to beg forgiveness from SUN-FUNG. While going for a drive in her car to chill out, CHI-TING bumps into CHIN-CHEUNG, so she decides to seduce him. SHEUNG-CHING invites SUN-FUNG and her family out for breakfast, following which SUN-FUNG notices CHI-TING holding CHIN-CHEUNG's hand and CHI-TING frankly admits that they are seeing each other. KING-WAI urgently calls CHIN-CHEUNG, claiming that a buyer is interested in buying some drugs from him; whereas SUN-FUNG immediately informs TING-MING about this after overhearing their conversation. While out on patrol, SUN-FUNG suddenly wants to go to the logistics warehouse, but KING-WAI refuses to go no matter what.… ...

KING-WAI has not returned home yet, but some police officers come to gather evidence, making TSI-CHING feel very worried. TING-MING gives a brief audio recording of CHIN-CHEUNG committing a crime to BING-YAN, who later gets attacked by the corrupt cop after arriving downstairs of his home. Luckily, TING-MING appears and goes to his rescue. SUN-FUNG discovers KING-WAI near his home, and just as KING-WAI is about to run away, KWUN-HUNG suddenly shows up to shoot and injure KING-WAI. After traveling back in time to April 1st, KING-WAI wakes up and finds himself at his sick wife TSI-CHING's bedside. SUN-FUNG and TING-MING track down KING-WAI to a warehouse, and suddenly they fall into the trap set up by KING-WAI. KING-WAI reveals that he just wants to live a quiet life together with TSI-CHING, hoping they will stay in the cave until April 4th.… ...

While drinking alone in a bar, TING-MING overhears someone mocking HAU-YUET, and he ends up getting into a big fight with that person. After the police arrive on scene, SHEUNG-CHING sees SUN-FUNG and TING-MING talking to each other and they seem to get along extremely well, so he cannot help having a strange feeling. Out of the blue, WING-JUN jumps off the building at the police station, and as a result, SHEUNG-CHING is invited by ICAC for an interview, during which he learns of WING-JUN's corrupt cop identity. Grief-stricken SHEUNG-CHING says he needs SUN-FUNG's support so proposes marriage to her, and she accepts. On the other hand, TING-MING suspects that WING-JUN was murdered because someone wanted to get rid of the witness. Having abducted CHIN-CHEUNG, TING-MING tortures him, forcing him to give the name of the corrupt cop, but CHIN-CHEUNG won't give him the name.… ...

During his conversation with the mystery person, CHIN-CHEUNG agrees to do the trade as soon as they kill TING-MING and SUN-FUNG, but the mystery person requests CHIN-CHEUNG to let SUN-FUNG go. CHIN-CHEUNG and CHI-TING return home and see SUN-FUNG, and it turns out that SIU-MEI asks SUN-FUNG to conduct an investigation as she is afraid that CHIN-CHEUNG might be harassed again. On one public occasion, CHIN-CHEUNG's non-indigenous resident identity is exposed by one of the villagers, UNCLE HENG, who even brings along CHIN-CHEUNG's mother to prove that CHIN-CHEUNG is not a descendant of the HO clan. Having learned of CHIN-CHEUNG's non-indigenous resident identity, BING-YAN refuses to continue to cooperate with him. Although SIU-MEI knew that CHIN-CHEUNG was not her biological brother a long time ago, she has been keeping the secret for the whole time.… ...

SUN-FUNG appears to be preoccupied while visiting TSI-CHING, and she tells KING-WAI that things would not go wrong like this had she not kept traveling back through time. KING-WAI brings some heavy firearms to TING-MING, so SIU-KEI asks TING-MING whether he decided to start a war with CHIN-CHEUNG. TING-MING replies that he simply adopted a strategy to maneuver CHIN-CHEUNG into becoming an enemy of the corrupt cop. Having heard this, SIU-KEI is thrilled with joy. When SUN-FUNG is getting ready to attend her engagement party, she receives a gift sent by TING-MING. She then asks TING-MING where he is now, but TING-MING just tells her to focus on her party. As the party starts, SUN-FUNG is the only one who does not show up, making SHEUNG-CHING so angry that he breaks into a furious rage. Meanwhile, SUN-FUNG arrives at the trade location to look for TING-MING, during which she is knocked unconscious by the corrupt cop.… ...

SHEUNG-CHING drives SUN-FUNG home, and he urges SUN-FUNG to ignore what TING-MING said. Following the arrest of LAT and the others, CHIN-CHEUNG needs to seek a new buyer; whereas TING-MING exposes HO-YUEN as the mole, with which CHIN-CHEUNG is very impressed. CHIN-CHEUNG runs into CHI-TING while leaving home, so he invites her to get in his car, during which he is attacked from behind and CHI-TING even takes a bullet for him. Going to the hospital to visit WAI-SING, SUN-FUNG accidentally overhears the most shocking secret outside of his ward. SUN-FUNG cannot get over the fact that SHEUNG-CHING shielded the corrupt cop, but SHEUNG-CHING, in his defence, states that he was so confused that he temporarily lost his way. Though TING-MING wants to expose SHEUNG-CHING, SUN-FUNG is of the opinion that they should give him a second chance.… ...

TING-MING informs SHEUNG-CHING that he has already found incriminating evidence against him, telling him to go to the warehouse immediately. While planting a hidden camera in the warehouse, he receives a call from his mother, who claims to be taken by someone to a shipyard. Though being trapped, SUN-FUNG is still worried about TING-MING. Surprisingly, after the door opens, she sees that TING-MING is all covered in blood, and they vow to never leave each other. At night, SUN-FUNG and TING-MING hold a campfire gathering, without knowing that SHEUNG-CHING carries a gun and comes to kill TING-MING. SUN-FUNG and TING-MING later return to the cottage, and TING-MING insists on going to deal with SHEUNG-CHING. However, SUN-FUNG locks TING-MING in the room, trying to fend off SHEUNG-CHING all by herself.… ...