Do-ki picks Cho Do-cheol up with his taxi and disappears. Maria, a girl from an orphanage, attempts to commit suicide from the Han River Bridge, and Do-ki comes to save her. He listens to her tragic story and decides to help her. Meanwhile, Ha-na tries to find where Cho Do-cheol went and realizes that there is something strange about the deluxe taxi he was in.

Do-ki manages to sneak into Ju-chan's factory and even orders their food products. As Do-ki and his team carry out the investigation, they realize that Ju-chan not only abused disabled workers but also committed frauds to embezzle more money. Meanwhile, Ha-na finds the deluxe taxi Cho Do-cheol took, but it was all burnt down.

Jung-min is a student who lives with his deaf mother. When he transfers to a new school, violence begins. Even though he asks for help from the school administrators and the police, there is no one to save him from this nightmare. Therefore, Do-ki disguises himself as a teacher to sneak into the school. Meanwhile, Ha-na receives an envelope anonymously and discovers a case.

No matter how hard Seung-tae tries to sabotage Do-ki, the Rainbow Deluxe Taxi crew manages to handle the situation with its fancy equipment. Furthermore, the three of them accidentally purchase drugs, and Do-ki stresses them out by threatening them. Therefore, Seung-tae decides to call someone for help. Meanwhile, Do-ki and Ha-na meet again at the meeting of Blue Bird members.

Do-ki wakes up from a nightmare after fainting on the street. Although everyone worries about his health, he still chooses to keep working without taking a break. Meanwhile, Do-ki gets his hands on the Seo Young-min case file. Ha-na also goes after this case despite Jin-woo's strict orders to drop it. Now, both Do-ki and Ha-na are after the cruel owner of U data.

Do-ki officially starts working at U data, the place where illegal videos are being shared. Once he figures out that the Strategic Planning Team is the core of the company, Do-ki does everything he can to get transferred there. Meanwhile, the abusive chairman Park Yang-jin wants to test Do-ki's overly zealous loyalty.

Jung-eun's suicide surfaces again, and her sister Go-eun gets a glimpse of what caused it all to happen. Sung-cheol and Do-ki do what it takes to bring justice to those involved. Do-ki finds a lead and heads straight into the heart of where it all began. Meanwhile, Ha-na asks Do-ki to be their informant.

Do-ki arrives at Park Yang-jin's vacation home. He starts to search for the data mine with the help of Go-eun, who finally returns. Meanwhile, Ha-na feels guilty that Jin-won is in danger and also heads to the vacation home to save him. Finally, U data's foundation begins to crumble when Do-ki reveals his identity to Chairman Park.

Ha-na finds Do-ki's employee identification card at Park Yang-jin's vacation home, or at least, what's left of it after the explosion. She believes that someone stole her suspect and tried to cover up the evidence. Meanwhile, Kyung-koo loses money to a voice phishing scam. When he goes to report it to the police, he realizes he is not the only victim.

Do-ki disguises himself as a burner phone peddler, Mr. Wang, from Harbin. Using his good looks, he tries to win the boss of the voice phishing ring's heart, Madam Lim. However, things start to get complicated when Ha-na arrives on the scene of their undercover operation and Jin-eon's cover is blown.

Ha-na closes in on Do-ki and the Rainbow Transport team. She decides to search Sung-cheol's house. Meanwhile, Do-ki meets the family of the victim in a murder case involving a missing body. When he finds out the suspect is Chairman Baek's man, he contemplates his next move. Just as Ha-na and Min-ho chase down the suspect, they walk straight into danger.

After Min-ho's death, Ha-na is determined to catch his killer. She succeeds in getting Gu Yeong-tae arrested since he is the lead suspect in this case. However, without any real evidence, the prosecution has no choice but to set him free. Ha-na goes to Do-ki, who has already been chasing Gu Yeong-tae, and asks for his help.

Do-ki finds Gu Yeong-tae while looking for the missing criminals. Ha-na asks Do-ki to hand over Gu Yeong-tae, but Do-ki plans an exchange to get the criminals back. Meanwhile, Sung-mi suggests to the criminals that they get their revenge on the Rainbow Transport team. The criminals each go looking for their own revenge.

The Rainbow Transport team faces off with Baek Sung-mi, Gu Seok-tae, and the criminals. Park Ju-chan rams a truck into the taxi that Jin-eon is driving, while Choi Min tries to film a video of Go-eun, just like he did with her sister Jung-eun. Do-ki decides that he can't stand by and watch his people get hurt anymore, and he sets out for revenge, burning with rage.

Sung-cheol and Do-ki decide to disband Rainbow Transport and stop getting revenge. Do-ki tells Ha-na all about what they used to do. However, a man claiming to be the killer of Do-ki's mom suddenly appears and says that the man who was previously arrested for the crime was a fake. Do-ki, who takes on one last case, must decide how to proceed.

The notorious serial killer Oh Chul-yeong turns out to be the actual murderer who killed Do-ki's mother and Sung-cheol's parents. Also, there is a man named Kim Chul-jin who had to serve 20 years in prison for a crime that Oh Chul-yeong committed. Despite Rainbow Transport's ups and downs, they decide to carry out their last revenge.