Actually, as soon as Qiu Tu had led his team into the Qin Family residence, Qin Zhengguang had already secretly investigated Qiu Tu.
After all, the arrival of a First Level Detective from the Political Department at his family clan was a political signal far too sensitive.
Adding to that, the rumors within the Bureau about "Qiu Tu holding old grudges against the Qin Family" made him exceedingly careful.
So, he meticulously looked into Qiu Tu.
He discovered that... Qiu Tu and the Qin Family had almost no interactions, nor any grievances.
This suddenly left Qin Zhengguang somewhat perplexed.
Therefore, he began to investigate the source of the rumors claiming "Qiu Tu bore a grudge against the Qin Family."
In the end, the investigation circled back to Yan Chen and Secretary Bai.