There has been no shortage of handover stories as Hong Kong prepares to mark the 20th anniversary of its return from British to Chinese rule on Saturday.

Journalists in the city have reported on every angle possible from the jaw-dropping HK$640 million (US$82 million) that the Hong Kong government has splashed out for celebrations surrounding the July 1 event to the tens of thousands of people expected to hit the streets in protest against their post-colonial masters in Beijing.

And we can’t forget the massive security detail (11,000 police officers, more than a third of Hong Kong’s 29,000-strong force) whose task it is to keep that army of protesters as far away as possible from President Xi Jinping during his three-day visit to the city to take part in the handover festivities.

This is what they have done on every handover anniversary since 1997.

Hong Kong’s last two colonial governors – David Wilson and Chris Patten – have weighed in on the city’s strengths and challenges going forward under Chinese sovereignty.

And Hong Kong’s first chief executives, Tung Chee-hwa and Donald Tsang Yam-kuen (jailed for 20 months earlier this year for misconduct in office), have also offered their perspectives.

Many a journalistic retrospective has been written and, as on that first rain-drenched handover night two decades ago, there has been much hand-wringing about the future of a city that values the rule of law and refuses to submit to the authoritarianism of the central government.

Hong Kong’s 20 years under Chinese rule – not to mention its 156 years as a British colony before that – is a fascinating and complicated story.

One can easily become lost in all the politics, the personalities and the lore. What can we look at to measure whether the city’s core freedoms of press, speech, assembly and religion that are guaranteed in its handover mini-constitution, known as the Basic Law will be maintained?

The city’s missing person’s list can be one simple gauge of whether Hong Kong’s special status will continue under the “one country, two systems” arrangement agreed in the Sino-British Joint Declaration of 1984.

That list has some alarming names, including the disappearance of the five Hong Kong booksellers from the city, mainland China and Thailand stirred international outrage in 2015. It is a case that still has not yet been resolved by Hong Kong authorities who are sworn and bound to protect its citizens.

All five men were associated with Hong Kong’s Causeway Bay Books, a now-defunct shop. It specialized in selling politically sensitive books banned on the mainland, and purporting to reveal the private lives of Chinese officials, among them President Xi.

Over a three-month period, the five – Gui Minhai, Lam Wing-kee, Cheung Chi-ping, Lui Por and Lee Po – went missing, only to resurface in mainland detention centers.

Gui, a Swedish national, was the first to disappear, apparently abducted by Chinese security agents on October 17 from his beachfront home in Pattaya, Thailand.

Later that month, Lam, Cheung and Lui would vanish while on the mainland. Before his disappearance on December 30, Lee, who holds dual Hong Kong and British citizenship, was last seen at his office in Hong Kong’s Chai Wan district.

Gui would resurface in January of 2016, offering a “confession” on state television in which he stated that he had returned to China to admit his involvement in a fatal 2003 hit-and-run accident.

The four others would also make what were widely seen as forced confessions of the roles they played in transporting banned books to the mainland for distribution and sale.

Gui remains in custody, but the four others were released following their confessions, obviously with clear instructions to remain mum about their time in detention.

When he returned to Hong Kong, however, Lam flipped the script on his handlers, calling a press conference on June 17, 2016, describing how he had been seized, handcuffed and blindfolded at the Hong Kong-Shenzhen border.

He also described how he was then transported to a secret detention center in the eastern city of Ningbo, where he was subjected to repeated interrogations without the assistance of a lawyer.

Lam’s explosive revelations placed the Hong Kong government, led by Chief Executive Leung Chun-ying, under enormous pressure to act on whether mainland security forces, who are prohibited from working in Hong Kong, had broken the law and violated the rights of the city’s citizens.

This is particularly so in the case of Lee, who appeared to have been abducted in Hong Kong and then transported across the border for interrogation.

Yet it’s been a year since Lam’s bombshell press briefing and no complaint has been filed and no action taken by the Leung administration, which has proven to be little more than a puppet regime whose strings are pulled in Beijing.

Leung’s successor, former chief secretary Carrie Lam Cheng Yuet-ngor, hand-picked by the central government, offers more of the same.

Challenged about the case of the booksellers in a CNN interview last week, Lam, who assumes office on July 1, replied: “It would not be appropriate for us to go into the mainland or challenge what happens on the mainland.”

But apparently it is appropriate for mainland security officials, clearly in breach of the Basic Law, to come into Hong Kong and waylay Hong Kong citizens before spiriting them across the border for secret interrogations and staged confessions.

A big question looming over Hong Kong as the spectacle of the handover celebrations draws near is whether the booksellers’ debacle was an isolated incident or, more frighteningly, represents a new lay of the land in a city where, nearly three decades before the Sino-British Joint Declaration is scheduled to expire in 2047, the “one country, two systems” mantra is gradually morphing into a “one country, one system” reality.

Even at the time of the booksellers’ abductions, Steve Vickers, the former chief of the Royal Hong Kong Police Criminal Intelligence Bureau who now heads his own political and corporate risk consultancy, Steve Vickers & Associates, told the American broadcaster CNBC: “[The booksellers’] case has grabbed international attention, but I’m aware of several incidents of a similar nature that have occurred.”

Vickers, whose company investigates kidnappings and engages in ransom negotiations, said he had been involved in “a series of other incidents involving booksellers,” but refused to disclose details due to privacy concerns.

More recently – and well beyond the shadowy world of illegally sold books on the mainland – billionaire Chinese businessman Xiao Jianhua appears to have been abducted earlier this year from his luxury suite at the five-star Four Seasons Hotel in Hong Kong’s bustling Central district.

According to reports, Xiao, who managed assets for a number of Communist Party officials and their relatives, left the Four Seasons at around 3am on January 27 accompanied by two female bodyguards and several unidentified men.

Some 12 hours later, records show the tycoon was driven across the border at the Lok Ma Chau border checkpoint. He has not been seen or heard from since, although there have been multiple reports tying him to mainland investigations into high-level bribery and stock market manipulation. There has also been speculation that he was holed up in Hong Kong to avoid arrest on the mainland.

A Hong Kong police request to Chinese authorities for information on his disappearance still remains unanswered today.

Of course, the wealthy Xiao’s probable detention on charges of being part of China’s massive web of corruption does not elicit the same sort of international sympathy granted to the lowly booksellers.

But for Hong Kong the broken constitutional principles appear to be the same: in both cases, agents representing the Chinese government, in violation of the Basic Law and the “one country, two systems” arrangement, abducted a person from Hong Kong – citizen, resident or otherwise –without any acknowledged agreement or even contact with local authorities.

As fireworks light up the sky over Victoria Harbor on July 1, that’s an ongoing worry for the people of Hong Kong.