Questions we might ask now: can influence be exerted in Sudan? Does the US, Britain and the rest of Europe have a responsibility to influence the Sudanese government? Absolutely. This is not an administration content to be an international pariah. But thus far there have been few adverse consequences for its actions in Darfur, few punitive measures. The US has proved that, when it wants to, it can have great and swift authority over the Sudanese government. It was the US, with Bush himself spearheading the process, that made a priority of negotiating a peace between the SPLA and Khartoum.

Why, then, are we moving so slowly and treading so gently with regard to Darfur? One possible explanation for Bush's apparent reluctance to intercede as quickly in Darfur as in southern Sudan is that there are hundreds of thousands of Christians in southern Sudan, whereas Darfur's victims are mainly Muslims. The war in Iraq has drained much of Bush's credibility abroad, and has clearly put a severe strain on his ability to negotiate for peace elsewhere. Perhaps most crucially, since 9/11 the Sudanese government has become an important ally - and source of information for the intelligence agencies - in Bush's war on terror. When What Is the What was published in the US, Valentino and I began to tour, feeling that its release coincided with a new and powerful wave of awareness and action directed towards Darfur. We spoke to students, to activists, to the informed and the uninformed.

One of our most trusted advisers in Sudanese affairs, John Prendergast of the International Crisis Group, told us that the worldwide temperature, in terms of pressure on the Sudanese government and awareness of the genocide, was at 101 degrees Fahrenheit. It needed, he said, to get up to 103. Then and only then, he said, would the genocide be stopped.

There were campaigns and protests around the country, and a range of innovative ways to hit Sudan's economic interests. Dozens of colleges divested from any holdings they had in Sudan, and cities and states followed. About 70,000 people removed their holdings from Fidelity, a mutual fund with holdings in China's oil interests in Sudan. Letters were written, congressmen were lobbied, films were shown, celebrities appeared on CNN. At the end of each talk we gave, Valentino and I implored the audience to do what they could to help Sudan generally and Darfur in particular. We offered the latest methods to make one's voice heard - including the most recent innovation, a phone number, 1-800-GENOCIDE, that linked directly to the White House switchboard. But as month after month went by, my own faith in what I was advocating began to diminish. I began to see change in Darfur as something perhaps beyond our grasp. I felt what I think many people felt at the time: utterly powerless, and quite close to without hope. Then, what might very well be the most effective tactic yet was unveiled by none other than Mia Farrow. I was aware of Farrow's work as an ambassador with the UN over the years, but I was unprepared for the editorial she wrote in the Wall Street Journal, on March 28, in which she made a connection that I had not heard before, and one that, at first, seemed a bit extreme. Because China is the major buyer of Sudan's oil, and supplies the Sudanese government with cash and weapons, it has been a focus of Darfur activists for a long time. Farrow knew that the Chinese are very much looking forward to the Beijing Olympics in 2008. They even asked Steven Spielberg to film the opening ceremonies. So Farrow wrote an open letter to Spielberg in the Wall Street Journal, noting that if he continued to work with the Chinese without holding them partially to account, he might "go down in history as the Leni Riefenstahl of the Beijing Games".

It seemed like an almost cruel gambit, but it worked. Spielberg was unaware of the connection between China and Darfur, and he was outraged. He wrote a letter to President Hu, urging action. President Hu dispatched his foreign minister, Zhai Jun, to meet with Sudan's president, Omar al- Bashir. No one knows what was said behind closed doors, but the meeting revealed China's Achilles heel. Khartoum has now agreed in theory to accept UN peacekeepers in Darfur, and there are other encouraging developments. If the temperature was at 101 a few months ago, it's certainly at 102 now. And I was happy to be reminded, by the cumulative effect of all these efforts, public and private, obvious and cunning, that every one of them matters.

People have asked Valentino if he knows what the What is, if now he feels any closer to an answer. He doesn't feel any closer, no, and I don't feel any closer, but for now it's clear we need to continue to focus on the tangible, on doing the tough but obvious work right before us.

With a peace in place since 2005, Marial Bai has been able to rebound - cautiously but measurably. Valentino's father has rebuilt his shop, there are cellphones everywhere, roads now connect the town to trading centres throughout Sudan, Kenya and Uganda, and optimism abounds. In July, Valentino will return, this time with more than a burdened conscience. He intends to listen to the needs of the people, and then meld their ideas with his plans to build a 300-student high school, a library, a community centre, a teachers' college. The plans go on and on. The school should be first, it's been decided - bricks are already being made and stacked. It's estimated that about 150,000 bricks will be needed, so the work ahead is clear. The wet season is on the way, so they're working quickly to do what they can before the rains come.