As a whole, this drama is quite good. A good story Sherlock Holmes-like with a fast paced plot so we don't really have the time to get bored. But there are a few very bad things that, I think, spoilt this drama.

First, it may be too fast paced. I would have liked that they sometimes spend more time solving a case because there's one case every two episodes and we don't really have the time to get involved in each and every case. Also, the killers are almost all very easy to guess.
Second, the romance was so forced that it was painful to watch. The two actors don't have any chemistry at all and they couldn't make me believe that they were in love. I don't know why they included this romance part of the story but I couldn't believe that Lu Yao had any feelings for Bai Youning. I honestly was more inclined to believe that he was still in love with his ex but they started this romance thing with Bai Youning at the same time as the return of the ex so it was really weird. The guy in love with his ex but is forced to love another girl. Also, making the ex the killer was a too easy way to get Lu Yao and Bai Youning together... I would have prefered him ended up with his ex, their story was more believable. And it is kind of sad that all the girls in this drama - that we only see a couple of episodes - have more charm and appeal than the FL...
Speaking of the FL, I didn't really have a problem with her until this romance thing. She was an okay character. Not the most useful one and quite annoying at times, but she brought something to the plot with her family background. It's a shame that they had to spoil her character by adding this romance thing with Lu Yao.

The romance part of the story really spoilt the drama for me. It appeared a bit out of nowhere and was really rushed (they kissed episode 29 or 30 and get married episode 36 while they started really flirting at episode 29 when Lu Yao's ex arrived in town). Also, they put aside the cases they were working on to develop the romance which was weird!! Especially the last case. Lu Yao starts investigating it, but then, he completely stops only to propose to Bai Youning and get married until Chusheng reminds him that he still has a case to solve! That was so weird to watch...

Anyway, I could go on and on about this romance catastrophe but I'm going to stop here.
I would still recommend the drama for the investigation part of the story and better skip the romance part.