The Muslim Brotherhood is the best-organised political movement in the most populous, most influential country in the Arab world.
What it does and what happens to it matters, both in Egypt and across the Middle East. The Brotherhood tasted power for just a year before its leader, Mohammed Morsi, was toppled by the country's powerful military.
Now, all the patience and discipline it is known for is being tested to the limit.
The decisions it makes in the coming weeks could mold the future of Egypt and of the region itself.
On the surface, it appears the Brotherhood has few choices. Individual members can choose to hide or speak out; to accept what has happened or to challenge it. Warrants have been issued for the arrest of many of its leaders. Morsi himself is in detention. Many are calling for the organisation's leaders to be tried for treason.
So, there is good reason for the Brothers to return to the way life used to be under Mubarak - swallowing their pride, biding their time, organising underground and waiting for a chance to return to power.
Many will not want to take this path. They believe they have been robbed of power; that their victory in a free and fair election has been tossed aside without any proper cause. Their anger is righteous, their sense of victimhood powerful.
There is evidence that many leaders of the movement are struggling to contain the anger of the rank-and-file Islamists who played the game of democracy and won, only to have their prize snatched from them.
The Muslim Brotherhood long ago renounced violence, but some of the leaders have called for an uprising to reverse what they describe as a military coup and restore Morsi to the presidency.
The prospect of a civil war looms, with many pointing to the example of Algeria in 1991, when the military cancelled the victory of the Islamists in an election only to see the country plunged into two decades of civil war that led to the deaths of hundreds of thousands.
The alternative for the Brotherhood is to do what Islamists did in Turkey in 1997 when the military intervened and ousted their government from power: they regrouped and returned stronger later.
If the Brotherhood is to retain one of its key strengths, it must make this choice - between violence or compliance - as a united body. The military and especially what's called the "Deep State" (the intelligence services, the police, the bureaucracy and judiciary), would like nothing more than to see the Brotherhood split and weakened.
In the shadows, groups linked to al Qaeda (which is led by the Egyptian Ayman al-Zawahiri) are likely telling the Brotherhood that their flirtation with democracy got them nowhere and never will. They are likely suggesting they should work to challenge the army, bring down the state and free their leader. One of these groups is Gamaa al Islamiya, once Egypt's most feared terrorist organization, which massacred 62 tourists in Luxor in 1997.
Morsi wooed Gamaa, appointing one of its members as governor of Luxor Province, one of the decisions that convinced many in Egypt that his presidency would be a disaster.
Nothing would suit al Qaeda better than to see the Brothers turn away from politics and consume the Arab world's most powerful country in violence. Few, though, believe the Brotherhood will take this path.
But if the Brotherhood keeps a cool head in inflammatory times and analyses what went wrong during the last year, it might learn a lot. There's no question it alienated large and important sections of Egypt's population.
Lacking the experience of governing and directing a major economy, it was accused of incompetence. It promised to govern for all Egyptians and did nothing of the sort.
Many of its decisions appeared to be for the benefit of the Brotherhood, not the country. It tried to rip up the constitution. It infuriated the judiciary. It alarmed Egypt's secularists and liberals, many of whom, while not voting for Morsi, were happy to see a freely elected democratic president. He just didn't rule like a democrat.
So, there are lessons for the Brotherhood to learn if they choose to. But there will likely be uncomfortable months ahead.
The Brothers may contest new elections next year. Or they may choose to boycott them. After all, once bitten, twice shy.
Islamists all over the Arab world will be watching their decision with interest. Many will have concluded from Egypt's example that political Islam's attempt to survive inside democracy and alongside a strong military doesn't work; that the key to victory is to seize power, by violence if necessary, and then to crush all opposition.
Egypt's new, temporary rulers have choices ahead of them, too. Banning the Brotherhood is one option. Almost certainly, that move would not kill the movement, only deepen its sense of injustice and resentment and stoke its desire for revenge.
And the West has choices, too.
At more than $1 billion dollars a year, no one in Cairo wants to lose such aid. A week after the overthrow of the president, the US announced it will deliver the promised supply of F-16 fighter jets to Egypt's military. But the Pentagon also announced Thursday that US aid to Egypt was formally put under review in the wake of the power shift.
In refusing to condemn the removal of an elected president, the West has already made a choice. A complex, messy moral compromise that it would rather have a new leader in the most important country in the Arab world than one seemingly determined to reshape his country as an Islamist power in a rapidly changing Middle East.