It could also be a fanfic that takes place in an alternate universe. In this universe, the events of 4x23 didn't happen as they did in the show. Maybe Beckett didn't become a detective in the same way, and Castle meets her in a completely different situation. They then start to solve mysteries together in this new setting.
A practical answer is Chapter 167, because it turns the idea into a concrete scene. The chapter opens with By the experimental field, Qi Tianyu was quite helpless as he watched Wen..., adds pressure through I'm not familiar with the others;
Look to Chapter 115 for the clearest answer. It begins with Jiang Yan was woken by a loud crowing noise., keeps building through Annoyed, he opened his eyes and saw that the hen, which should have been..., and lands on [Pure bystander, wasn't Jiang Yan known as a notorious playboy?.
The best chapter pointer here is Chapter 151, "He Yun is quite good, but we are not fated to be together". It opens with Now it was Zhang Cheng's turn to be confused. and closes on I will have my assistant pay the bill.. The reason it matters is that the chapter closes with Was he...
The best chapter pointer here is Chapter 107, "Are You Really Going to Participate in That Variety Show?". It opens with On the plane, when He Yun had taken off his mask and greeted her... and closes on Although Su Yinwan's recent change in temperament had been hard for her to....
The best chapter pointer here is Chapter 118, "Director Sun, When Did You Get a Barrage Above Your Head?". It opens with At 8 in the morning, several guests appeared on time next to the... and closes on Hearing this, both Jiang Yan and Shu Yan started to complain as well..
A practical answer is Chapter 166, because it turns the idea into a concrete scene. The chapter opens with Only after everyone in the small courtyard had left, did Zhao Lang stride..., adds pressure through Fans can't bear to watch anymore.], and ends on However, after interviewing the villagers.
If you want the clearest chapter reference, go to Chapter 121. Early on, Seeing that Wen Jiaojiao's condition had improved significantly, Director...; later, the chapter leans on A doctor, donned in a white coat, hurriedly got out and immediately asked....
A practical answer is Chapter 92, because it turns the idea into a concrete scene. The chapter opens with Jiang Li, lightened from any task, had plucked a few leaves from the..., adds pressure through Just as Jiang Li was about to refocus and continue expanding her..., and ends on Finally, someone.
A practical answer is Chapter 147, because it turns the idea into a concrete scene. The chapter opens with Xiao Xueyi nodded in agreement after listening., adds pressure through She even took the initiative to call?, and ends on Only Jiang Li glanced back at Director Sun, and then took out her.
Look to Chapter 113 for the clearest answer. It begins with The next day, Jiang Lili was up before dawn as usual., keeps building through But this time was different; as she got dressed and opened her room door,..., and lands on If things are really as you say, that is indeed quite serious..