Hang Seng opened 2.09 percent lower on Friday, according to Xinhua. Hong Kong reopened while mainland markets and Stock Connect stayed shut until October 8, per investinglive. Futubull then had Hong Kong bank stocks sliding, with Standard Chartered down more than 5 percent.

The lawsuit is the other half of the arithmetic. The Daily Star reports a $2.7 billion suit against Standard Chartered over its alleged role in the 1MDB fraud. My sources give me the headline number and the allegation, not the plaintiff's pleading, so the figure is a claim and not a finding. (A claim does not need to be right to move a share price on a day with no one else trading.)

Right, the thin session matters. With Stock Connect closed, there is no mainland money on the other side of the book. Southbound flow, the usual buyer of last resort for Hong Kong banks, is absent until the connect reopens. A stock that falls more than 5 percent against a market down about 2 percent is carrying its own news, and the sell side had no one to hand it to.

For a regulated firm in Hong Kong the lawsuit points at one instrument. The AMLO (Cap. 615) and the HKMA's AML/CFT guideline cover customer due diligence, record keeping and suspicious transaction reporting for authorized institutions, and the Enforcement and AML Department supervises them. Nothing in today's notices from that department touches Standard Chartered. The HKMA's published items this week are statistics, a sandbox update and the half-yearly stability report.

The next dated event is October 8, when Stock Connect reopens and the first southbound orders show whether Friday's 5 percent was news or just an empty room.