The story so far: Mexico, traumatised by the assassinations of a Roman Catholic cardinal in 1993 and a ruling party presidential candidate in March 1994, is rocked by a third murder on 28 September last year. Mexicans suspect political rivalries or multi-billion dollar drug business is behind all three killings. The September victim, Jose Francisco Ruiz Massieu, was secretary-general of the Institutional Revolutionary Party, brother of the country's deputy attorney-general and a former brother-in-law of then President Carlos Salinas de Gortari.
Mr Salinas appoints Mr Ruiz Massieu's brother Mario, until then head of the country's anti-narcotics drive, to investigate the murder. Mario Ruiz Massieu resigns two months later, saying senior PRI officials are blocking his investigation. Last month, the new attorney-general arrests Mr Salinas's brother Raul and charges him with masterminding the Ruiz Massieu killing. The attorney-general does not mention Carlos Salinas in the case, but hints that the former president may have tried to keep a lid on investigations into an earlier murder, that of PRI presidential candidate Luis Donaldo Colosio in March 1994.
A furious Mr Salinas, already disgraced because his economic policies have collapsed, at first goes on a hunger strike, demands an apology, gets one and breaks his fast. The attorney-general then stuns the nation by calling in Mario Ruiz Massieu for questioning for allegedly hiding evidence himself.
Mr Ruiz Massieu is next seen in the United States, where he is arrested by customs officials at Newark airport and charged with failing to declare the $46,000 he is carrying with him. Mexican officials admit they tipped off the Americans, and say Mr Ruiz Massieu was planning to flee to Europe. Mr Ruiz Massieu, pictured wearing a combat flak jacket over his suit after his court appearance, counters that he fears for his life and requests political asylum in the US.
The Mexican government dropped a new bombshell yesterday when it claimed to have evidence that Mario Ruiz Massieu had links with Mexico's biggest drug-smuggling gang, the so-called Gulf cartel, believed responsible for the final land leg of Colombian narcotics shipments to the US. He is thought to have deposited up to $25m (£15m) in US bank accounts during the period May-November 1994, when he was first Mexico's anti-narcotics chief, then chief investigator into his brother's murder, "an official source" told the Washington Post newspaper.
If true, such charges would inevitably point the finger back to Carlos Salinas. For one thing, Mr Salinas appointed Mario Ruiz Massieu. If Mr Ruiz Massieu was covering up for Raul Salinas in a murder case, could the president have been in the dark? Second, the Salinas brothers had always remained close, despite Raul's reputation as a ruthless businessman who became a billionaire through the PRI and his brother's position. If Raul Salinas ordered the killing of Jose Francisco Ruiz Massieu, why? And if there was a logical motive, would Carlos Salinas not have suspected his brother?
Perhaps, you might say, but a man would not condemn his own brother to life imprisonment. By the same token, however, the Mexican authorities' latest investigations are suggesting Mario Ruiz Massieu protected his own brother's killer, or even knew of it in advance and was bought off.
Many Mexicans agree with Mario Ruiz Massieu's lawyer that the scenario being pushed by the attorney-general is hard to swallow. Could the whole thing simply be an attempt by President Ernesto Zedillo to discredit his predecessor and win back some semblance of control over a disillusioned nation? Or even if the allegations against Raul Salinas and Mario Ruiz Massieu are accurate, was not Mr Zedillo, hand-picked by Carlos Salinas, part of the same system last year?