Zhongjin Capital Management made a splash in the past couple of years in Shanghai. The wealth management firm's imposing branch office on Shanghai's historic Bund pulled in many eager investors seeking the double-digit returns it promised on short-term financing products. It had a big profile, sponsoring popular Shanghai TV dating program "Saturday Date" and signed up domestic billiards star Pan Xiaoting as a spokesperson.

But this past week, the image of riches and success that it had cultivated came crashing down. Police said they arrested 21 executives linked to Zhongjin Capital on Tuesday on suspicion of "illegal fundraising," a loosely defined term applied to irregular behavior in China's energetic but opaque shadow banking sector.

The only person named by Shanghai police so far has been top executive Xu Qin, who local media said was arrested at Shanghai's airport on his way to get married in the Vatican. Xu has been described by domestic media as a high roller, who is under 30 years of age.