During his patrol, Lei Zin Kiu comes across a man putting up posters about an alien invasion. Despite his superior's mockery, he continues chasing down leads and soon discovers the hidden agenda behind the whole charade, which will change his life forever after his encounter with Cheung Nok Hang and Chan Ka Hei, two Slashers from a detective agency.

After learning that her dad leaves her a detective agency, Ka Hei goes there for the first time, only to be greeted by a stranger she met on her birthday. While Ka Hei is still feeling lost in life, this very stranger helps to light the path for her. Meanwhile, Lei Zin Kiu has to decide on his next move when his superior deliberately picks on him for reasons unbeknownst to him.

After quitting his job, Zin Kiu works as a bodyguard for Mr. Mo, a wealthy man who has just woken up from a five-year-long coma. After waking up from a coma, Mr. Mo is determined to confess to Zan Zan, a hairstylist, that he was going after before he fell into a coma. Little does Mr. Mo know that everything has changed and Zin Kiu is caught up in a dilemma again.

After much deliberation, Chi Kiu decides to join Unlimited Slash Limited and works undercover to help stop Mr. Mo from confessing to Zan Zan. When Chan Yau Shing breaks the news of his engagement party, which will take place in a month, the trio has to work fast to make Mr. Mo give up on Zan Zan. However, they are put in a bit of a dilemma when Mr. Mo suddenly shows up at their office.

Mr. Mo convinces the trio to help him win Lei Zan Zan over and the three of them come up with a plan to ruin Chan Yau Shing's engagement party. But little does Chi Kiu know, Nok Hang and Ka Hei accept a commission to help one other person and that it is all just a charade. When a lady asks for their help, the trio sets out to unearth the mystery behind the case.

The unsuspecting trio goes to a client's house to help investigate a case. But little do they know that the client's daughter is an acquaintance of Ka Hei. With two different versions of the story, everyone is deeply skeptical about the whole case. But Ka Hei is determined to investigate and get to the bottom of things.

Losing someone close in life drives Ka Hei to despair as she regrets the words left unsaid and deeds left undone. Both Nok Hang and Chi Kiu stay by her side to help her through the challenging times and they both take care of the business while she tries to get back on her feet. Not wanting to be left alone, Ka Hei moves into the office to help Nok Hang with his problem.

A young girl has come seeking help from the trio to help manage her social media account in hopes that she'll land her dream job as an editor. Meanwhile, Ka Hei finds comfort in Nok Hang's company and she continues living in the office with him on the pretext of helping him with his sleepwalking disorder. Chi Kiu, on the other hand, tries to expose Nok Hang's lies.

Just when Chi Yui decides to quit her job, she runs into her crush that she met a long time ago. So Chi Yui goes to the trio again to ask for their help to transform her life which gives people the wrong impression of who she really is. When that guy finally asks Chi Yui out on a date, the trio has to think on their feet to help her get through it.

Green with envy, Chi Kiu moves in to live in the office with Ka Hei and Nok Hang. Now that the trio is living together, they have to find a way to resolve their disputes. Again, Chi Yui shows up to ask for another favor to help her keep up her facade to the bitter end. Meanwhile, the trio is greeted with surprise when Prince Harry shows up at their doorstep.

Nok Hang soon realizes that his new client, Prince Harry, turns out to be Chi Kiu's little brother, who flees from the UK and travels back to Hong Kong himself. While Prince Harry is out to give out flyers, he bumps into a triad leader, Tai, who then becomes a client of Unlimited Slash Limited, commissioning them to find his long-lost son. Chi Kiu feels uneasy as he realizes that his dad keeps a huge secret from him.

After Tai finds out that Chi Yui is his son, he insists on taking him away, but the trio convinces him not to rush things. When Chi Kiu's dad, Big Head Buddha, shows up at the office, they learn the truth which puts them in a dilemma. After 15 years, Big Head Buddha and Tai finally meet again, but things take an unexpected turn when Chi Yui stumbles upon a file.

After Chi Yui learns that he is Tai's son, he decides to follow in his dad's footsteps and to take over the Thai Heng Group. To stop Chi Yui from walking down a path of no return, Big Head Buddha, who is at his wits' end, has no choice but to come clean with Tai. If this incident has taught Ka Hei and Chi Kiu anything, it's that they should be true to themselves.

Knowing that his dad will soon return to Hong Kong, Nok Hang starts looking for a house and makes preparations to welcome his dad. However, everything requires money and Nok Hang is desperate to bring in new cases for the company. While he's out giving out flyers, he comes across a man, Mr. Lau, who asks for his help investigating his wife, which leads to a dispute between the trio.

Nok Hang discovers the truth behind Lai Hing's affair, but it puts the trio in yet another dilemma as they wonder whose side should they take. Ka Hei comes clean to Lai Hing about her relationship with Lau Chun, and Lai Hing convinces her to help her keep her secret. Meanwhile, Ka Hei runs into someone she least expects to at Lai Hing's wedding anniversary party.

While Nok Hang and Chi Kiu wait for Ka Hei on Valentine's Day, a man shows up at the office asking for their help to find his missing girlfriend. Ka Hei receives a call from Lai Hing requesting a meetup and learns of Lai Hing's decision. Later on, Ka Hei talks to her mom and finally hears the truth after all these years.

After all these years of waiting, Ka Hei is happy that her mom is finally back in Hong Kong, but learning the truth breaks her heart. Nok Hang and Chi Kiu try to cheer Ka Hei up by picking a date they believe is the perfect date to celebrate Ka Hei's birthday this year. However, Ka Hei finally loses it when both of them force her to choose one of them. She walks out on them only to find herself walking into another disaster.

Realizing that Ka Hei is missing, Nok Hang and Chi Kiu search high and low for her. Ka Hei's mom shows up at the office, and together, the three of them set out to the place where it all began to find Ka Hei. When the police arrive at the scene, the trio once again reveals a shocking truth about the person behind Lam Yuen Yuen's death. After the whole ordeal, one of the guys decides to step out of Ka Hei's life.