MOSCOW -- Within 10 days of Boris Nemtsov's killing on a bridge near the Kremlin, five Chechens were locked up in a Moscow jail. The suspected triggerman had confessed, according to investigators, and said he acted on behalf of a man known as Rusik -- a nickname for Ruslan. He and another suspect said Rusik had promised them each 5 million rubles ($72,000) and provided the cheap compact car allegedly used in the crime.
It was sketchy and shrouded in disinformation, but a narrative emerged with remarkable speed after Nemtsov, a prominent opposition leader and fierce foe of President Vladimir Putin, was shot dead late on February 27 while strolling home from a cafe with a girlfriend from Ukraine.
Soon, that picture filled out further when media reports implicated a senior security official in the North Caucasus republic of Chechnya, Ruslan Geremeyev.
And then the momentum slowed. For months, nuggets of information and disinformation have leaked out through the media in dribs and drabs, creating a clutter of fact, fiction, and rumor that has done little to advance the case. Meanwhile, there have been setbacks: Suspected gunman Zaur Dadayev swiftly withdrew his alleged confession amid claims that he was tortured, and the lead detective on the case was replaced in May.
Nemtsov, a former deputy prime minister who published studies alleging massive corruption surrounding Kremlin projects such as the 2014 Sochi Olympics, was working on a report about Russia's involvement in the war in eastern Ukraine when he was gunned down at age 55 -- the highest-profile assassination in a nation that has been plagued by political killings since the 1991 Soviet collapse. Putin said on March 4 that his slaying cast "shame" upon Russia.
Six months later, though, the investigation has become a skirmish in a broader battle for power and influence between federal law-enforcement authorities and Ramzan Kadyrov, the former rebel fighter Putin has relied on for years to maintain order in Chechnya amid an Islamist insurgency that erupted in the North Caucasus following two devastating separatist wars.
The outcome, Nemtsov's allies fear, may be the same as in other killings of government critics during Putin's 15 years in power: at best, the triggerman and accomplices convicted, but no clarity on who was really behind the crime, and a strong suspicion that the trail leading to the mastermind went cold because it got too close to the Kremlin -- or Kadyrov.
After the 2006 killing of Anna Politkovskaya, an investigative journalist who exposed corruption in Moscow and human rights abuses in Chechnya, it took eight years and two trials to convict the men accused of committing the crime, and nobody has been charged or even identified as the suspected mastermind. Nobody has been tried for the killing of Natalya Estemirova, a rights activist who was abducted in Chechnya and shot dead in 2009.
This time, the investigation got off to a fast start. But it has a huge hurdle in pursuit of Geremeyev, whom lawyers for Nemtsov's family consider key to advancing the probe and following the trail to the "zakazchiki" -- those who ordered the hit.
Despite indicating their intention to do so in April, investigators have been unable to even question Geremeyev. He has disappeared, prompting claims that he is being protected by Kadyrov.
Vadim Prokhorov, the Nemtsov family lawyer, believes that only Putin is in a position to allow investigators through this impasse.
"It's still unclear if there is political will to find and catch Geremeyev and Mukhudinov," he told RFE/RL, referring to Geremeyev's driver, who has been described in media reports as a suspected accomplice.
Even if those two men are tracked down and prosecuted, Prokhorov suspects that is where the trail will end.
"It is obvious, unfortunately, that they are not going to take this further – higher up than Geremeyev and Mukhudinov," Prokhorov said. "But we will fight that."
It will be a tough fight, if it comes to that.
Putin set the bar as low as possible in public comments early in the investigation, preparing the country for the possibility that the authorities might never determine who was behind Nemtsov's killing – if anyone.
Lauding law enforcement agencies for rapidly catching the five Chechens, and calling them "the killers" rather than suspects, Putin suggested that those who carried out the slaying may have been acting on their own accord rather than following orders.
"I don't yet know whether they will manage to get the people who ordered it and whether there are people who ordered it," Putin said in a televised phone-in with the nation on April 16. "This will become clear in the course of the work that is currently under way."
For many Russians, the notion that Nemtsov's killers acted alone is laughable. But that was one of the main theories touted by federal investigators from the outset, when they suggested he could have been killed because of his "position" on the Islamist militant attack that killed 12 people at the office of French satirical magazine Charlie Hebdo in January -- which he condemned.
Kadyrov also put that forward as a possible motive, saying in early March that Dadayev was a pious Muslim who was shocked by the magazine's cartoons of the Prophet Muhammad.
In the same Instagram post, Kadyrov called Dadayev, whose service as former deputy head of the Sever battalion he praised, "a true Russian patriot."
Against that background, allies of Nemtsov have pushed to move the investigation forward.
On April 22, Nemtsov's family lawyers formally requested that the federal Investigative Committee question six senior Chechen officials and lawmakers over the assassination, including Geremeyev and Kadyrov himself.
The very next day, the dangers of this line of enquiry were brought home by media reports as it emerged Kadyrov had instructed an auditorium full of top Chechen police officials that their men should "shoot to kill" any law-enforcement officer from elsewhere in Russia who enters the region unannounced. "They have to reckon with us," he warned.
Kadyrov's order was ostensibly prompted by a killing that was unrelated to the Nemtsov case.
But the message was clear.
In an April 27 note to Nemtsov's lawyers, which was seen by RFE/RL, investigators said they would seek to question Geremeyev -- but not Kadyrov or the others. The lawyers, it said, had "not indicated specific circumstances that they think are significant for the investigation."
The investigators also declined to answer a pointed question: Is Kadyrov obstructing the investigation?
Earlier this month, Nemtsov's daughter Zhanna Nemtsova filed a complaint challenging the refusal of investigators to question Kadyrov and the other high-ranking Chechens. Calling the decision "illegal and unfounded," her lawyer said that Kadyrov is acquainted with the detained suspects and "may have information" about the organizers of her father's killing, according to state news agency TASS.
In their April appeal, the lawyers noted that Nemtsov and Kadyrov had crossed swords at least three times.
The first was recounted in Nemtsov's 2007 book Confessions of a Rebel, in which he said he had been threatened by Kadyrov in Chechnya to such a degree that Kadyrov's father Akhmad, then leader of the republic, deemed it necessary to provide Nemtsov with a "gigantic" security detail to escort him to safety in neighboring Ingushetia.
In May 2014, Nemtsov formally complained to the Federal Security Service (FSB) about Chechen men claiming allegiance to Kadyrov fighting alongside pro-Russian rebels against Kyiv's forces in the conflict in in eastern Ukraine.
Less than two months before his killing, Nemtsov criticized Putin in a blog post for allowing the Chechen leader to grow as powerful as he has. The trigger: a December 28 event in which Kadyrov gathered some 20,000 camouflage-clad men at a soccer stadium in Chechnya's capital, Grozny, and declared them to be Putin's personal "military infantry."
"We ask the national leader of Russia to consider us a voluntary special force of the supreme commander-in-chief prepared to protect Russia, its stability, borders, and carry out any military task of any difficulty," Kadyrov said from a podium.
WATCH: Ramzan Kadyrov Presents Putin's Personal 'Military Infantry'
Such displays do not sit well with the Russian security agencies, many of whose members share widely held concerns about the clout of Kadyrov. It is a rare instance of solidarity between the "siloviki" and Kremlin critics -- like Nemtsov -- who say Putin has let Kadyrov run wild in exchange for his iron hand in Chechnya and a fierce loyalty that they fear may be temporary.
If the investigation into Nemtsov's killing is a test of how far Putin will go to protect Kadyrov, it is clear he has not reached his limit.
"Ramzan is directly and overtly protecting Geremeyev and this blocking the vital next stage in the investigation. Putin is indirectly and implicitly protecting Kadyrov, blocking any chance to get round the Chechen stonewall," Mark Galeotti, a New York University professor and expert on Russian politics and the security services, wrote earlier this month in the online magazine Russia!
With few signs of Kremlin pressure on Kadyrov to cooperate, investigators have turned to subtler methods -- such as media leaks that have fueled public scrutiny of his ally Geremeyev and the detained suspects -- to advance the case.
Recent reports in the influential newspaper Kommersant and the news site Rosbalt described how investigators were trying to dig up dirt on Geremeyev's uncle Suleiman, a member of Russia's upper parliament house, in order to coax Geremeyev out of hiding.
Galeotti said such reports show how law-enforcement agencies, hamstrung by politic constraints, may be trying to ratchet up pressure in the case.
"This investigation is surprisingly open," he said. "And it has really shown not just the limits of genuine law enforcement in Russia, but that there are also people trying to do genuine law enforcement in Russia and trying to find subversive ways round the political constraints that are put on them."