When a farm laborer in this hardscrabble village in northern India went to the police last week to report that his daughter and her cousin had gone missing, a constable slapped him in the face and sent him away.
Hours later he found the two girls, hanging by their necks from a mango tree. A post-mortem found they had been raped.
Three men were arrested for the crime in Uttar Pradesh state that underscored the enduring culture of sexual assault in India and the capacity for appalling violence between Hindu castes. Two policemen were held on suspicion of attempting to cover up the killings.
One of Modi's biggest challenges will be making a break from the ineffectual responses of governments to heinous crimes like this and the gang rape and murder in December 2012 of a young woman in the capital, which provoked a rash of street protests, much of it over the authorities' apparent indifference.
"When these incidents occur, like the one in Delhi in 2012, there is public outrage," said Meenakshi Ganguly, South Asia director of Human Rights Watch. "Then the state responds, but it gets left behind at the level of rhetoric."
On Monday, Modi's Bharatiya Janata Party sought to make political capital. Workers from the party accused the Uttar Pradesh state government, headed by a rival party, of negligence over the crimes and of being unfit to govern.
Police fired water cannon at the protesters, who were demanding the state government be dismissed and the imposition of direct, presidential rule.
Four of the five suspects arrested in last week's case are from the powerful Yadav community, a land-owning Hindu caste that holds political sway in Uttar Pradesh. Police declined to confirm reports that three had confessed.
The victims were, like Modi, from a lowly caste. They were Shakyas, by tradition peasant farmers who are often vulnerable to exploitation by the Yadavs.
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"The nature of it shouts out caste atrocity," said Kavita Krishnan, a prominent women's rights activist and left-wing politician. "It's meant to have a terrorizing effect."
Caste divisions, baked into society over generations despite official efforts to remove them, could be as much a problem for the prime minister as the tensions between Hindus and minority Muslims that critics fear he could inflame.
Critics fault Modi, a Hindu nationalist, for pursuing a majoritarian agenda: More than two-thirds of his cabinet ministers belong to a powerful Hindu grassroots movement, raising doubts that he can close social rifts and govern in the interests of all Indians.
While inter-caste violence is an age-old symptom of social oppression, it is also a sign of social change as marginalized groups seek democratic rights and a share in India's rising prosperity.
"There's a sense of changing India," said Krishnan, seeing in the violence "a need to reinforce caste hierarchies".
After the two young cousins were raped and strung up in Katra Shahadatganj, villagers refused to let their bodies be cut down until the men they accuse of the killings were arrested.
Images of the girls - still roped to sturdy branches, a crowd gathered below - went around the world, transforming what would have become a forgotten crime into a symbol of sexual and caste oppression in India's most populous state.
It was just after 7 p.m. on Tuesday when an uncle of the girls heard their cries as he was coming in from the fields.
He flashed a torch and spotted four men, recognizing one. He confronted them, but fled after being threatened with a handgun, he told Reuters on Saturday at the victims' family home.
The uncle and the girls' father went to the local police post to report the girls missing. Indian law does not allow rape victims and their relatives to be identified by the media.
There, they were asked their caste and told that the person the uncle had recognized by torchlight was an "honest man".
"I fell to their feet," said the father, pleading with them to find his daughter and niece. That's when he was slapped.
"They said the girls will reach your home in a couple of hours," said the father, lying outside his cramped brick house, his face a mask of grief and exhaustion.
Katra Shahadatganj is a dirt-poor village like so many in Uttar Pradesh, the northern state in the Ganges river basin that is home to one in every six of India's 1.2 billion people.
Its roads are potholed, and green sludge courses through open sewers. Power supplies are sporadic, medical facilities are feeble and teachers rarely turn up at the local school.
Surender Sakhya, a farmer from a nearby district, said the Yadavs get protection from the police.
"And it's not just police, but political parties," he said, complaining that Yadavs steal the crops of many farmers.
All five suspects were being held in a jail in the nearby town of Budaun. A guard and three other officers said it was not possible to talk to the men.