Castle, 62, habitually sits at the head of a long table, farthest away from the entrance. Ranged on either side of him last Friday were 17 senior executives, foreign and Indonesian, from some of Indonesia's biggest companies.
Everyone knows Jim Castle. He is big and cheerful and a pillar of the Jakarta business community - an optimist when it comes to the country he has lived in since his Peace Corps days in the 1970s. Some of that optimism may have died on Friday morning when a lone suicide bomber walked into the lounge and blew himself up, killing four of Castle's suited guests and injuring him and 13 others.
There seems no question that the small gathering was specifically targeted. Closed-circuit television footage shows the bomber, a backpack strapped to his chest and dragging a small Samsonite carry-on, emerging from a lift. He turns left and, without hesitation, walks towards the lounge. Then he disappears from view, there is an explosion of debris, and smoke pours out of the corridor into the lobby.
If he had turned right, he would have found himself heading for the Sailendra coffee shop, the target of the past suicide bombing on August 5, 2005, which killed 12 people, including a Dutch banker.
Castle, who owns an apartment adjoining the hotel, was in the hotel during that attack too. Because he was sitting at a table on the upper level of the two-tier restaurant, the blast wave from the car bomb passed over his head. He was shaken, but unhurt.
The windows at the back of Castle's apartment were all blown out, and I remember how impressed he and his Japanese wife, Ikuko, were that the hotel management repaired them so quickly. The damage from the July 17 explosion is going to take longer to repair - physically, mentally and economically. That was clearly the intent. After all, why go after a small business gathering when the bomber could have caused far more casualties in the coffee shop?
He had checked in as a paying guest two days before the attack, enough time to select a target that would not involve killing a large number of Indonesians, as had been the case in the past.
It was those at the end of the table who died because they were nearest the blast. New Zealander Timothy Mackay, the president-director of cement-maker Holcim Indonesia, three Australians and two hotel staff never had a chance.
Gene Galbraith, chairman of the board of commissioners of Bank Central Asia, is habitually late to these gatherings and always sits at the end. But on Friday morning, he had made a prior breakfast appointment with several stockbrokers.
"Only now, is it starting to sink in how lucky I am," he told me the following morning as we exchanged notes on the condition of the businessmen, most of them personal friends, who are recovering in Jakarta and Singapore hospitals.
Among them is David Potter, Freeport Indonesia's long-serving chief geologist and the founder of Grasberg, the world's most profitable copper and gold mine, in the Central Highlands of Papua. Potter, a burly Vietnam veteran, was medivaced to Singapore with a badly broken leg and abrasions. So was former Freeport chief executive Adrianto Machribie, who has facial burns and a shrapnel wound in the stomach.
Consultant Noke Kiroyan, former head of Rio Tinto's Indonesian operations, who was seated close to Castle, suffered damage to his eyes. Andrew Cobham, former head of Motorola's Jakarta office, has a broken ankle and severe bruising.
Castle has lacerations and hearing loss, but his young associate, Max Boon, was the worst of the injured. He had his left leg amputated below the knee, and 24 hours after the explosion, was reported to be unconscious in intensive care.
Economist Umar Juoro would have been there. But he was in Singapore for the week - staying at the Marriott, as it happens. He wanted to get back for the weekly session, but he had a budget air ticket he could not change.
As Juoro and everyone else has noted, it had all been going so well - with Indonesia free of terror attacks - before last week's bombing broke a four-year hiatus and put the country back on the map. Castle was delighted that President Susilo Bambang Yudhoyono won the July 8 election and was looking forward to real progress over the next five years, particularly with Indonesia avoiding the full brunt of the economic crisis.
The president had been basking in the afterglow of his stunning first-round victory before the bombing. Gripped by a cold fury, his eyes often lifting to the heavens, he raged against those who he said had destroyed "the peace and security of the nation".
Indonesians had never seen their normally reserved president like this. At one point, he seemingly linked the bombings to his political opponents. At another, he hinted that it was the work of established terrorist networks.
"Maybe some of them have committed crimes, assassinations or murders, and escaped justice," Dr Yudhoyono said on the palace grounds. "But this time, we will not let them act like Dracula and angels of death."
The president's anger was understandable. Someone had rained on his parade, and he was not going to take it lying down.