North Korean leader Kim Jong-un has not been seen in public for more than two weeks, missing commemorations for a key political anniversary, and reports he underwent a cardiovascular procedure have spiralled into speculation he could be incapacitated or even dead.
Both Seoul and Washington have played them down, but there has been no concrete proof of life in Pyongyang's state media, beyond reports of messages sent in his name.
AFP looks at some questions and answers on what could happen if Kim, the third generation of his family to lead the North, died.
How would the world learn of his death?
The North is extremely secretive, and doubly so about its leadership. Kim's father and predecessor Kim Jong-il had been dead for two days before anyone outside the innermost circles of North Korean leadership was any the wiser.
On past precedent, the first indication will be an announcement of a special broadcast on state television. If the camera cuts to a woman in a black dress, Kim is dead.
Ri Chun-hee, the North's veteran newsreader, has for decades announced key milestones in the North, with her voice brimming with joy for successes and tears flowing for bad news.
When she declares a successful nuclear test or missile launch, she wears a pink joseon-ot, a traditional Korean dress known as hanbok in the south.
But she wore black to reveal the deaths of both Kim Jong-il in 2011 and his father and predecessor, the North's founder Kim Il-sung in 1994.
Will there be another Kim?
The North is officially known as the Democratic People's Republic of Korea but has been ruled by members of the same family since its foundation in 1948.
The claim to legitimacy of the Workers' Party is founded in Kim Il-sung's fight against Korea's Japanese occupiers and later the US-led United Nations forces during the Korean War.
The party maintains extensive control of society -- "Single-Minded Unity" is one of the North's most enduring slogans -- and no-one expects any kind of popular uprising in the event of Kim's death.
"North Korean generals and top politicians will not start fighting for power or it will be a limited fight for power and they will accept a new leader who is likely to be somebody of the Kim family," said Andrei Lankov of Korea Risk Group.
Who are the contenders?
Kim is said to have three children -- only the gender of the second one, a girl, is known -- but they are far too young to take over.
His sister Kim Yo-jong is one of his closest advisers, acting as his envoy to the South's Winter Olympics in the South, accompanying him on his diplomatic forays and recently issuing political statements in her own name.
She is an alternate member of the politburo of the ruling Workers' Party, and currently the most prominent of Kim's relatives, but the North is socially conservative and has never had a woman leader.
Kim's eldest half-brother Kim Jong-nam -- who could traditionally have expected to inherit -- was brazenly assassinated in 2017, smeared with a deadly nerve agent at Kuala Lumpur's international airport in a killing most analysts say could only have come from Pyongyang.
Kim has an elder full brother, Kim Jong-chol, who is known to be an Eric Clapton fan and has shown no political ambition.
There is also Kim's wife Ri Sol-ju, who has enjoyed a higher public profile than her predecessors and was given the title of First Lady in 2018.
Any other notables?
Kim Pyong-il, his father's half-brother -- the Kim family tree is complicated by several of its members having a series of wives or consorts -- was the North's ambassador to several eastern European countries for decades.
But he was recalled to Pyongyang last year from the Czech Republic, his most recent posting, and has not been heard of since.
What about candidates from outside the family?
Kim is not known to have designated a successor but officially his number two is Choe Ryong-hae, a member of the ruling party's top decision-making body -- the Presidium of the Political Bureau -- and first vice-chairman of the State Affairs Council, the country's top government body.
He is hugely powerful, and he may also be related to the Kim family by marriage: it has never been confirmed whether Kim Yo-jong is married, but South Korean media have previously reported, citing unnamed sources, that her husband is Choe's son.
What would happen to the body?
Both Kim's father and grandfather lie embalmed in the Kumsusan Memorial Palace of the Sun, a sprawling mausoleum complex of marble-collonnaded halls on the outskirts of Pyongyang.
Kim would probably be similarly preserved before Pyongyang put on a state funeral with all the pomp and circumstance it could muster, around 10 days after his death. (AFP)