The killing of Russian opposition figure Boris Nemtsov within sight of the Kremlin has exposed rarely seen tensions between different camps inside President Vladimir Putin's system of rule.
No outsiders can know with any certainty what is happening behind the red-brick walls of the Kremlin, but some of Nemtsov's associates say his shooting is being used by one faction to send Putin a message that they are unhappy and need to be reckoned with.
That would represent a challenge to the foundations of Putin's 15-year-old rule, built on a rigid pyramid of power and the assumption of unshakeable loyalty.
“I think that perhaps Putin, even completely sincerely, was bewildered and even afraid,” Vadim Prokhorov, Nemtsov's lawyer, said of the hours after the February 27 shooting.
“Because if you can do that next to the Kremlin, then is it not possible to do it along the route of the (presidential) motorcade?” he told Reuters.
Feeding a mood of frenzied speculation in Moscow, Putin this week canceled a planned trip to Kazakhstan without explanation. A Kazakh official said Putin was ill, while the Kremlin said he was fine and working as usual.
Who is on which side in this rivalry, or even that such a rivalry exists, is impossible to establish with complete confidence because no one has publicly acknowledged any serious differences between camps.
Yet analysts point to signs of tensions between, on one side, the powerful head of Russia's Chechnya region, Ramzan Kadyrov, and on the other, the Russian state security agencies that are Putin's closest associates.
Nemtsov, a 55-year-old former deputy prime minister who had become a vocal critic of Putin, was shot dead as he walked home with his girlfriend after dining next to Red Square. He was the most prominent of a string of Kremlin critics to be killed since Putin came to power; in many cases the gunmen have been jailed but the masterminds remain unidentified.
Many of Nemtsov's supporters said the president stood to gain by removing a relentless critic. Russian officials denied involvement and Putin called the killing a shameful tragedy.
A timeline of events in the 13 days since Nemtsov was shot points to a tangle of conflicting accounts, confused messages and rival narratives from usually deferential media.
That messy picture jars with the meticulous stage management normally associated with the Kremlin.
Kadyrov put forward the theory that Nemtsov was killed by a group of Islamists because he had publicly defended Charlie Hebdo, the French magazine attacked by militants in January for publishing cartoons of the Prophet Mohammad.
That version has been contradicted by evidence, possibly obtained from surveillance, published in Russian media. One paper said one of the two men charged in the killing, Zaur Dadayev, was tailing Nemtsov months before the Jan. 7 attack on Charlie Hebdo.
Nor has Kadyrov's version of events been backed up by state investigators. They have refused to comment on the alleged motives of the two men they charged over the killing, or the three people they are holding but have not charged.
The suspects in detention are from Muslim Chechnya, but that does not make them Islamists. There have been numerous cases where police have accused Chechens of acting as hired gunmen in high-profile killings.
Usually, when an issue is important to the Kremlin, officials are meticulous in making sure mainstream media outlets follow broadly the same script, according to Russian journalists who have been exposed to this treatment.
Sergei Sharov-Delaunay, an aide to Nemtsov in the opposition movement, said he had a number of theories about the motive for the killing, but one is that it was part of an internal power struggle.
“It might have been some group within the authorities trying to put pressure on Putin, to boost their position, to force even more radical scenarios,” he told Reuters.
Kadyrov, the Chechen leader, professes loyalty to Putin but also represents a risk for him. Kadyrov put down an anti-Moscow insurgency in Chechnya, helping Putin cement his rule. In exchange, Putin gave him a large degree of autonomy to run his region as he chooses.
The arrangement has so far been successful for both men, but some observers say Kadyrov is overstepping the mark. Russian media have reported incidents of police in Moscow having run-ins with Chechens, then coming under pressure not to prosecute them because of their ties to Kadyrov.
“If Putin is able to put Kadyrov in his place, then that will sharply improve his standing in his immediate entourage, something he is in great need of,” said Georgy Satarov, who was a senior aide to the previous president, Boris Yeltsin.
There are signs, too, that Putin's nationalist allies, who include some senior people inside the government, are getting fractious.
While Putin's intervention in Ukraine has angered the West, for some at home he has not gone far enough.
Many wanted Russia to help expand further the territory held by separatist rebels in southeast Ukraine, to include all of the Luhansk and Donetsk regions. Large swaths of those mainly Russian-speaking regions are still controlled by Kyiv.
The best-known Russian commander among the separatist rebels in eastern Ukraine, a former special forces officer called Igor Girkin, has accused Putin's entourage of betrayal.
“The team that the president is now working with is absolutely pro-Western,” he said in January on Neuromir TV, a Russian Internet TV channel. “It is the same people that the West is counting on as the fifth column.”
In December last year, at a news conference in Moscow, a Reuters reporter asked Putin if, given the pressures from the crisis in Ukraine and the sputtering Russian economy, he felt at risk from a palace coup.
Putin replied: “I can assure you that we don't have palaces, so a palace coup isn't really possible. The official presidential residence is the Kremlin. It is well protected.”