The blackened, windowless hovel that saw the deaths of hundreds

Juvenal is the son of the prophet Joseph. He takes me to the blackened, windowless hovel at the back of the family farm in this remote outpost of rural Uganda.

It was here, he says, that his father, Joseph Kibwetere, defrocked Catholic priest and leader of The Movement for the Restoration of the 10 Commandments of God, abused his followers' children, some as young as three. Here, while Theresa, Kibwetere's wife, looked on helplessly, began the pattern that culminated in the massacre on St Patrick's Day of up to 600 of his disciples in Kanungu church.

Only now, when the the toll has reached 924, a notch ahead of the Jonestown massacre in Guyana two decades ago, is the scale of the suffering of Kibwetere's followers emerging. Yesterday a fifth mass grave was found near the remains of the church but until international assistance arrives in Uganda, there will be no more exhumations.

Juvenal, 36, is eager to open closed doors. As we stand in the heat beside the makeshift jail, he tells me how 60 children at a time were kept there. "They lived in the poorest camps, with no bedding, lots of skin diseases and very little food. They had to use their own torn clothing, and some were naked. Even three-year-olds had to work the fields."

New cult members were prevented from seeing the children. Apart from heavy manual labour, the children were not allowed out - "They were made to relieve themselves in a basin."

Juvenal brings me into the family living-room, decked with photos of the young priest, who at one point was also a school inspector. Joseph Kibwetere, suspected mass-murderer, looked out from the pictures, sitting shyly by his wife and later posing in crucifix and cassock.

When I meet Theresa Kibwetere, what this witness to so many secrets wanted to talk about was not her husband, but the woman she believes possessed him. Credonia Mwerinde, she says, was de facto cult leader. Mrs Kibwetere says that when police sought clues to the murders, they took a book Mwerinde published in 1997 outlining the credo of The Movement for the Restoration of the 10 Commandments. In it she says she was a former prostitute who had slept with children and priests.

Non-members of the church were satanists; members had to be punished to get them to Heaven. She believed children were sinners and made parents watch her mete out violent punishment. Mwerinde said Ugandans were the chosen people in the promised land and that Aids was divine punishment. She detailed how the world would end over a three-day period, though those who "got through the shift" would survive, own beautiful things and have new knowledge.

I ask Mrs Kibwetere to describe her husband's relationship with Mwerinde, who moved into the family home with two other "priestesses" in 1989. By 1990 Kibwetere was sharing his bedroom with the three women and his wife.

Juvenal shifts in his chair, then shows impatience: "I don't want to hide these things; my mother was used." He says his father had a sexual relationship with Mwerinde. As his mother sits quietly in her chair with a grandchild on her knee, Juvenal openly tells me she was "very much under the influence" of the cult. She was one of the original "12 apostles".

Something stirs in Mrs Kibwetere. She frequently looks down at her granddaughter. Her words confirm - one or two sentences behind - what her son is telling me. When she describes how Mwerinde started abusing her children, she talks rapidly and holds her grandchild tightly. Mwerinde caned her children, and beat her 12-year-old daughter until she suffered head injuries. During the beatings she would make Kibwetere watch in silence - "I couldn't stop her, because my husband was present."