What started with the shock defection of dozens of government ministers and MPs to the opposition is now going to the country's supreme court.

PNG is known as ‘the land of the unexpected’ and there could be many more twists ahead as the turmoil plays out.

Here's what you need to know about the unfolding political drama in Australia's nearest neighbour.

When PNG's parliament opened a week last Friday, more than half of the members were missing and several government benches were notably empty.

Around 10 minutes into the session, the opposition dramatically entered the chamber, with dozens of government ministers and MPs among their ranks.

It became clear a push to oust prime minister James Marape was underway — rumours had been swirling for months about dissent in government ranks, but the shift was sudden.

The opposition used its swelled ranks to take control on the floor and adjourn parliament until December when a vote of no confidence in Marape could be held, and a new government potentially installed.

While it happened quickly, Geejay Milli, a lecturer in political science at the University of Papua New Guinea, said it wasn't entirely surprising.

There are restrictions around when a vote of no confidence can happen, and once it's possible, it's open season.

"To achieve political stability in Papua New Guinea has been really challenging in the last 45 years," she said.

Opposition leader Belden Namah claimed 61 of the parliament's 111 members were now in his camp, and that "as far as the numbers are concerned, the new government is here."

Despite calls from the opposition for him to resign, Marape dug in, saying he believed he could get enough MPs to return to his team before a vote of no confidence in December.

"At the moment, I'm comfortable," he said. "We've got four weeks; four weeks is a lifetime in politics."

Amid the upheaval, Australia's prime minister Scott Morrison cancelled a planned trip to PNG.

The disgruntled ministers and MPs who crossed the floor have offered a range of reasons for doing so.

Concerns over PNG's troubled economy, which was struggling before the Covid-19 pandemic and has only worsened since, have been a major factor cited by many.

"Revenue for next year is projected to be K12.9 billion while expenditure is projected to be its highest ever in PNG's history, a level of K19.6 billion," University of Papua New Guinea economist Maholopa Laveil told Pacific Beat this week.

"The budget deficit for next year is the highest planned deficit of K6.6 billion."

The government has said it was handed an economic mess and has been working to repair it.

Marape came to power promising to get a bigger slice of resources revenue and to make PNG the "richest black Christian nation".

But progress toward that lofty goal has been slow.

The government's tough negotiations have led to the temporary closure of a major gold mine in the country's highlands, which has also been criticised by the opposition.

The Porgera mine stopped operating in April after Marape's government refused to renew operator Barrick Niugini's lease — the profitable mine produced more than eight tonnes of gold last year.

"Over 80% of our economy depends on the resource sector, when you mismanage that the economy obviously suffers," former prime minister Peter O'Neill said.

"No-one in their right mind shuts down an operating gold mine when the prices are at the top of its peak."

O'Neill is a prominent member of the opposition bloc, which points to another factor at play: political rivalries. He lost the leadership to Marape in similar circumstances last year.

Marape, for his part, has described the opposition as wanting to "maintain the status quo of corruption, big boys elite politics [and] multinational lobbyism", arguing his government was "changing [the] country's policies and laws for a better future".

How did the government then suspend parliament for five months?

When a vote of no confidence is afoot in PNG politics, the two sides go into camps.

Each side sets up in a hotel, where their MPs all live while they wait for the vote. It allows them to keep track of their numbers and plan their next steps.

With Parliament seemingly adjourned until December, the Opposition went so far as to fly out of Port Moresby: a charter aeroplane took the team to Vanimo, on the other side of the country, to wait it out.

Then, the next shock move. While the opposition was out of town, the speaker of parliament ruled that their adjournment was "incorrect" because according to the law, only a government minister can suspend parliament.

"The result of my decision is that the meeting of the parliament … is still in progress," he said.

The following morning the government's remaining MPs returned to parliament alone, while the opposition was still out of town.

With no-one to oppose them, the government passed its budget and suspended parliament until April next year.

While that was all happening, O'Neill was at the court house on behalf of the opposition, trying to get an immediate order to adjourn the sitting.

He wasn't able to do that, but he has already lodged another application with the supreme court trying to have the sitting ruled illegal.

Is this normal in Papua New Guinea?

In a sense, yes — votes of no confidence are just part of the political landscape in PNG.

They're common enough to be almost predictable if you're handy with a calendar.

When a government changes in PNG, either through a vote of no confidence or an election, the new government gets an 18-month grace period where they cannot be challenged through a vote.

Marape took power at the end of May last year, and his grace period was set to expire at the end of this month.

PNG's parliament is made up of several small parties, so holding a coalition together to rule can be challenging.

This latest upheaval has even split some parties — with some of their MPs going to opposition and others staying with the government.

"[Votes of no confidence] create a very dynamic space where there is the potential to seize political power from parties and from groups," said Dr Bal Kama, an expert on PNG constitutional law at the Australian National University.

"Once that plays out in parliament — sometimes in a way that is not legal — the issue ends up in the courts."

Sometimes, the results can be dramatic.

One court ruling in December 2011 effectively left PNG with two prime ministers — the supreme court ruled that the election of O'Neill four months earlier was unconstitutional, and called for former leader Sir Michael Somare to be reinstated.

S omare had been receiving medical treatment overseas for months, and the opposition — which was also led by Belden Namah back then — declared that the position of prime minister was vacant due to Sir Michael’s long absence.

The supreme court ruled that the subsequent vote in parliament, which resulted in O'Neill's election, was illegal: however, O'Neill still had the support of most MPs, leading to a months-long power struggle between the two men.

O'Neill's party then won the most seats at the 2012 election, and he continued as prime minister until last year.

With another supreme court battle looming, chairman of the constitutional and law reform commission Kevin Isifu took out a full-page advertisement in local papers saying he wanted to see changes to how PNG elects its prime minister, "given successive constitutional crisis".

"It is time people must directly elect prime ministers so that he or she focuses on managing the business and affairs of the country, instead of looking for resources to maintain numbers to stay in power," he wrote.

Now the court battle gets underway, with both sides claiming the other broke the rules.

Thankfully, PNG's courts have had a lot of practice dealing with these sorts of political controversies.

"They have dealt with similar issues in the past," Dr Kama said.

"The judges are quite familiar with the importance of the issue, the sensitivity of the issue, and how to go about bringing a decision that is consistent with the law."

Kama said it would be interesting to see how the courts decide, as in his view, both sides had potentially broken the rules.

The opposition's decision to adjourn parliament appeared to be a breach of standing orders, but the government's decision to recall the parliament in the opposition's absence may also have been against the law.

If the opposition's challenge is successful, parliament could be back in December — if not, it will be back in April.

Either way, a vote of no confidence in Marape will still be possible: the main difference will be how long each side gets to bolster their numbers before parliament returns.

For the moment, Marape is remaining in the top job, and he is saying "it's business as usual".

But he still doesn't appear to have a majority of the 111 members. When his team returned to parliament, there were only 50 MPs.

Ms Milli from the University of Papua New Guinea said there could be a lot of movement of MPs between the two camps in the weeks ahead.

"It's difficult to predict how people move back and forth, but it is expected — there should be some movement."

The opposition camp isn't giving up.

Former deputy prime minister, Sam Basil, who was one of the defectors, on Friday said the opposition was maintaining the numbers to take power.

"We are confident that we will walk into parliament on 1 December and we will conclude from the adjournment we made last week. I can say, the [new] government is here."

In addition to its supreme court challenge about the legality of the last sitting of parliament, the opposition leader Namah also has a long-running court case challenging the validity of the vote that saw Marape become prime minister back in May 2019.

It's unclear who the opposition will put forward as its alternate prime minister if it gets a chance. There are several members of its ranks, including some of those who recently crossed over, who would like the job. That decision could affect the numbers.

Even if the parliament remains adjourned until April, a vote of no confidence remains a real possibility.

But if a week is a long time in politics, five months is an eternity.