By Paul Moss
BBC News, Lebanon
Muhammad sips his coffee, takes a few staccato puffs on his cigarette and leans forward furtively as if to share some important secret.
UN official concede that conditions in Sabra and Shatila are appalling
He has a nervous energy - he is a nervous guy.
As a teenager back in 1982, Mohammed saw his family killed in the notorious Sabra and Shatila massacre, when Lebanese Christian Phalangists attacked Palestinian refugees.
Twenty three years later, he is still living in the same camp.
"I'm frightened, frightened to death. If we are disarmed, who's going to take care of us?," he asks.
"We were disarmed once before, and look what happened!"
Muhammad's anxiety has been aroused, or rather re-awakened, by the political developments now playing out on the streets of Beirut.
Up to half a million demonstrators at a time have come out calling for Syria to pull out of Lebanon in line with UN Security Council Resolution 1559.
The resolution also demands the disbanding of Lebanon's armed militias, which focuses attention on the powerful pro-Syrian Shia group, Hezbollah.
Lebanon, those in favour of resolution 1559 argue, needs to become a normal country, not living under foreign occupation, and without armed groups operating as a state within a state.
But that raises the question of what should happen to its Palestinian population, plenty of whom are heavily armed.
There are several hundred thousand Palestinians in Lebanon.
They are the survivors and descendants of those who fled Israel at its creation in 1948, and again after the 1967 war.
Today, they live in conditions which UN officials will tell you are appalling, even by the grim standards of the refugee diaspora.
Their camps often lack basic amenities, while their inhabitants are largely blocked from making a decent living in the host country.
At the Ein al-Hilweh camp, armed Palestinian militias patrol their respective micro-territories, sometimes engaging in internecine conflict in a microcosm of the Palestinian world.
Shootings are common, but when somebody is killed, the Lebanese authorities do not intervene. Indeed, they rarely enter the camp at all.
List of enemies
The Christian politician Dory Chamoun speaks for many Lebanese when he denounces this state of affairs.
"It's about making Lebanon a proper democratic republic where laws are respected and where the only weapons that are authorised are in the hands of the police and the army," he says.
"I don't see any reason whatsoever for the Palestinians to have arms."
Some of the refugees in Beirut's refugee camps have been there since 1948
But plenty of Palestinians do.
They collected an impressive list of enemies during the 1975-1990 Lebanese civil war - Phalangists, the Israelis, the Shia Muslim Amal militia.
Although the Lebanese Civil War ended 15 years ago, some smaller Christian militia have units which remain armed and prepared for action.
One commander recently showed off his collection of guns to Western journalists.
He insisted his men would never use them on other Lebanese people because he did not want to go back to civil war.
But if the Palestinians ever seemed to pose a threat, he said, well that was a different matter.
And it is not just jumpy militiamen in the hills who believe in such a threat.
In the fashionable bars of central Beirut, you hear people once again describing the Palestinians as a potential enemy living in their midst.
Everyone is waiting to see if Syria attempts to put down the demonstrations, and one theory has it that they will get the Palestinians to do their dirty work for them.
It is a fanciful suggestion. Palestinians have little love for Syria, which turned on them during the Civil War. And there is also base self-interest at work.
If Syrian troops pull out, many Syrian labourers will leave too, vacating their jobs, perhaps for Palestinians to fill.
But this is a situation of suspicion and counter-suspicion.
And although many Lebanese retain a deep sympathy for the Palestinians and their cause, the more sectarian-minded see them as mortal foes.
Back in Shatila, Muhammad is weighing up his chances.
He says he does not trust the Lebanese government, or even his own leaders right now.
Like many Palestinians in Lebanon, he suspects that Palestinian Authority President Mahmoud Abbas might cut a deal with Israel, one that sorts out the West Bank, Gaza and Jerusalem, but pays only lip service to the refugees' claim of a right to return to their homeland.
In this state of heightened collective anxiety, he is not in a mood to think about laying down guns.
"The strategy has always been to erase the Palestinians from the map of Lebanon," he argues.
"Amal killed 1,000 civilians because we were defenceless. And the friend of today can easily become the enemy of tomorrow. History repeats itself."
Muhammad insists his main goal in life is to go back to Palestine, the land his parents fled.
But right now, he just wants to be anywhere but where he is.